Friday, September 18, 2009

USES IN WAN


Today, the optical fiber is widely used in France, Europe and in the world. In France and Europe, we can mention the network that LDCOM comprises 11,000 km of fiber connecting 60 cities. By using WDM and SDH, it and can reach speeds of several hundreds of Gbit / s. Extended ends by MAN, the network now extends Spain, Italy and Switzerland. At the global level, the intercontinental routes are in perpetual changes to withstand the ever-changing traffic. Today, the recent work of the CNET (National Center for Studies in Telecommunications) on the show that soliton transmission can be push the limits inter-amplifiers. A soliton a very short light pulse which propagates without remarkable deformation of its shape or change its speed. This phenomenon has been noticed for the first time as a wave in a channel, but it exists in many fields, including light. Thus, one can use a very wide bandwidth with transmission speeds Agenda pétrabit per second or one million gigabit per second. The pulse modulation is based on the coding of the pulse corresponding to a logic with two or three levels. This technology has been used by MCI-WorldCom, which reached a speed 10 Gbit / s over 900 kilometers and CNET, in March 1999, which transferred data at a rate greater than one terabit per second  1000 km via a conventional optical fiber. The fiber seems to be the medium of the future in the relationship long distances.

Sunday, September 6, 2009

The use of SONET and WDM

Today, the use of SONET and WDM multiply. Indeed, coupled use of these two technologies yields networks Optical integrating the strengths of SDH: transmission reliability and management bandwidth. These networks are currently expanding throughout the world and examples are more numerous


However, researchers are trying to reduce the stack
protocols used to arrive in all-optical solutions. Could
then see soon arrive networks constructed as follows:



Researchers are also set for challenge to achieve the "Optical
buffer "or other words to store the light ...

The return of alarms

SDH allows the sky to achieve the alarm on the various equipment. These alarms correspond to different problems could exist on the equipment or connections.
Major alarms are:
• AU-AIS (Administrative Unit Alarm Indication Signal)
• AU-LOP (Administrative Unit Loss of Pointer)
• HP-UNEQ (HO Path Unequipped)
• HP-RDI (HO Path Remote Defect Indication)
• LOF (Loss of Frame) Frame Loss
• LOS (Loss of Signal, drop in incoming optical power level
causes high bit error rate.) Loss of signal
• LOP (Loss of Pointer) Loss of Pointer
• LP-UNEQ (LO Path Unequipped)
Olivier ADAMUS SONET / WDM
Johann COPIN
Eric Panetta IR3 - 2003
22/30
• MS-AIS (Multiplex Section Alarm Indication Signal)
• MS-REI (Multiplex Section Remote Error Indication)
• MS-RDI (Multiplex Section Remote Defect Indication)
• OOF (Out of Frame)
• TU-AIS (Tributary Unit Alarm Indication Signal)
• TU-LOM (Loss of Multiframe)

Wednesday, September 2, 2009

Equipments of SDH connections

Major equipment
There are 4 main categories of equipment to make connections SDH:

Switch card: This card provides the functions of multiplexing and circulating traffic between line interfaces and other interfaces. Its capacity is equivalent to 12x12 STM - 1, without limitation ( "non-blocking matrix"). This card can be split to ensure protection.

The line cards (STM-1, 4.16 ..): These cards provide optical transmission signals STM. They are not split. The failure of one of them does not the protected traffic as it is transmitted simultaneously interfaces on the "East" and "West".

The multiplex controller module: this card provides the functions of central control and safeguard the configuration. It is not split because its failure does
not disrupt traffic.

The communication card: This card provides the functions management to network management. It is routed through the signal STM online. This map is not split because its failure does not disrupt the traffic.

Tuesday, September 1, 2009

The SONET frame and security

The SONET frame is composed of 9 rows. The first three bytes of each row contain information synchronization and supervision. Similar to SDH, we find the principle of adaptation-related encapsulation of data in virtual containers

Security


Different techniques can secure the use of SONET / SDH; these techniques are mainly access control and encryption, conventional solutions. Cons attacks format by inserting data specifically constructed, jamming is an excellent technique, at least in theory.

However, SONET and SDH are nevertheless sensitive to some uses flawed, as the inclusion of escape sequences. Has priori, these limits are not really security problems
Major: they can cause denial of service on the network, and degradation of the service should not be significant (depending In reality, the type of connection available to the attacker). In conclusion of this it is said that using SDH and SONET safely is realistic, complex attacks to work is very high.

Sunday, August 30, 2009

Differences between SONET and SDH

The hierarchy of the standard SDH corresponds to that of SONET for ATM interfaces.
The hierarchy of flows is different on three continents (USA, EC, Japan) is a rate of 51.84 Mbps, which was chosen for form the first level of SONET: STS-1 (Synchronous Transport Signal, level 1). The other levels are called SONET OC-n (Optical Carrier level n). So there is just a gap between the levels of SDH and SONET: Level 1 SDH (155.52 Mb / s) is level 3 and level SONET 2 of SDH (622.08 Mb / s) is the level 12 of SONET.

The virtual containers and types

To carry signals, using virtual containers (VC: Virtual Container). In the VC that are sections overload (POH: Path Overhead), which are used by pointers. The transport of containers on STM 1 STM 16 done by TDM. The couple VC-pointer, called AU (Administrative Unit) can therefore to carry both synchronous signals. Depending on the speed, the units are two levels Possible AU3 and AU4. Containers are managed in the SDH transmission network, regardless of the signals they carry. This packaging is called adaptation.

Types

There are two types of virtual containers:

• The virtual containers of lower order (VC-11 VC-12, VC-2
and VC-3) which are carried in virtual containers
higher order.
• The virtual containers of higher order (VC-3 and VC-4)
are multiplexed to form the resulting signal.

Saturday, August 29, 2009

The principle of SONET / SDH

The arrival of SDH

SDH offers significant advantages over the PDH. SDH based
on a digital frame that provides high level, in addition to the top
speed (higher than PDH):
• Greater flexibility as to the possibility of extracting or
to insert directly a component of said multiplex
• Ease of operation and maintenance (Flow
important for these functions)
• An opportunity to move towards high speed (frames
synchronous broadband are built by multiplexing
phase the basic entity. This entity defines the basic
implicitly all frames high speed, the limitation
is more than technological)

• An interconnection of broadband systems facilitated by the
normalization of the frame line and optical interfaces
corresponding
• The network architectures providing security against
the line faults or equipment
• The modularity of SDH equipment is more suited to
advances in technology.



The SDH frames

There are different frames in SDH. The base frame is called
STM-1 (Synchronous Transport Module level 1).
STM-1 to a length of 2430 bytes. Frequency transmission
is 125ns, which gives us a rate of:
2430 * 8 / 125 = 155.52 Mbit / s.
In this frame, 9 bytes are reserved for the management and
addressing, leaving a payload of 150.336 Mbit / s.

Saturday, August 22, 2009

OBJECTIVE OF TRAFFIC GROOMING

1.To combine low-speed traffic streams onto high-capacity wavelengths
2.Improve bandwidth utilization
3.Optimize network throughput
4.Minimize the network cost (transmitter, receiver, fiber link, OXC, ADM, amplifier,wavelength converter etc)

TRAFFIC GROOMING

Traffic-grooming is a kind of multiplexing in optical signal by packing low speed traffic streams into higher-speed streams.

There is a significant advantage to groom the traffic.
1.Reduction of wavelengths : If each demand requires a light-path exclusively, we need a lot of wavelengths to be allocated.
2.Reduction of costs for installing WDMs and operating networks

SONET

The evolution of flows of different services, the need for flexibility transmission network, the need to improve the functions of exploitationmaintenance, the continuous increase of transmission capacity on fiber optics and the need for interconnection between operators to high flows and Standardized have shown the limitations of the current hierarchy and led to standardization.


SONET or SDH?
Research on SONET lead each time on another Technology: SDH (Synchronous Digital Hierarchy). It should be clearly introduce the origins of SONET and the links between SONET, PDH (Plesiochronous Digital Hierarchy) and SDH.

Introduction to SONET
SONET (Synchronous Optical Networks) is an initial proposal Bellcore, which defines the transport layer of a physical architecture broadband. SDH (Synchronous Digital Hierarchy) is a vision specific SONET, requested by the Europeans and adapted to the ATM. We will focus our research rather SDH which is used in
Europe and more media on the internet. However, the differences between these
two technologies are very slim.

PDH to SDH


PDH is the technique that preceded SDH. It consists of multiplexer and carry bits of the lower flow transmitting at rates higher. The lower rates are high at a value higher order of bits of justification, with an indication of their presence in the resulting frame. The flow is not exact multiple of the returns but slightly more. It is what was described as plesiochronous (in Greek, Plesio = almost plesiochronous = almost synchronous). The main shortcoming of this technique is that multiplexing does not have access to information in a way directly without demultiplex all channels.

For example, to provide a line to 2Mbit / s more multiplexing and demultiplexing must be made to extract a fast channel 140Mbit / s. It was a defect in telephony but acceptable for use on optical networks, it becomes unacceptable.

Saturday, August 15, 2009

CWDM optical multiplexing

In CWDM equipment, we can use lasers in unregulated temperature, lower cost and which emit at wavelengths spaced 20 nm in the transmission window 1270-1610 nm. CWDM is the subject of the ITU-T recommendation G.695, which provides for flexible and scalable solutions, including the solution of 8 to 16 channels with two optical fibers (one for each direction of transmision), offering data rates of 1.25 Gb / s to 2.5 Gb / s per channel.

However, systems CDWM not compatible with optical amplifiers, are limited in scope. Two lengths are indicative of connection specified in Recommendation G.695: up to 40 km and up to about 80 km, which is usually enough for the needs of metropolitan networks.

In contrast, in the record books in 2004, Alcatel was just topped mythical 10 Terabit / s, in a multiplex fiber Alcatel TeraLight 256 channels each operating at 40 Gb / s over a distance of 100 Km This error-free transmission was achieved by combining amplifiers hybrid Erbium / Raman.

In addition, Alcatel has managed to pass 3 terabit / s over a distance of 300 Km 7, in 300 multiplex channels each operating at 10 Gb / s, with optical amplifiers doped with erbium (EDFA) broadband

ITU-T G.692 (Optical interfaces for multi-channel systems with optical amplifiers)

Recommendation ITU-T G.692 (Optical interfaces for multi-channel systems with optical amplifiers) has defined a comb of wavelengths allowed in the only window of 1530-1565 nm transmission. It normalizes the spacing in nanometer (nm) or Gigahertz (GHz) between two wave lengths permitted the window: 200 nm or 1.6 GHz and 100 GHz or 0.8 nm.

The technology is called dense WDM (DWDM) used when the spacing is equal to or less than 100 GHz. Systems at 50 GHz (0.4 nm) and 25 GHz (0.2 nm) to obtain respectively 80 and 160 optical channels.

For even lower densities, we refer to U-DWDM: Ultra - Dense Wavelength Division Multiplexing. Thus, systems
10 GHz (0.08) to obtain 400 optical channels.

Systems WDM / DWDM most marketed today include 8, 16, 32, 80 optical channels, which can reach capacities of 80, 160, 320, 800 Gb / s through a flow capacity of 10 Gb / s. You can reach a capacity of 4 000 Gb / s (4 Tera b / s) with 400 optical channels at 10 Gb / s, U-DWDM technology.

One of the key components of WDM / DWDM amplifier is the erbium-doped fiber (EDFA) which can compensate for losses due to insertion multiplexing / demultiplexing wavelengths.

However DWDM introduces non-linear phenomena which have the effect of limiting in practice the distance between amplifiers between 50 and 100 Km:

- Crosstalk between channels (XPM: Cross Phase Modulation),
- The blend quatre ondes (FWM Four Wave Mixing) which created the inter-modulation between the different optical channels,
- The Raman effect (SRS: Stimulated Raman Scattering), which increases the received power differences between channels and therefore produces a too large dispersion of the signal to noise ratio.

Over singlemode optical fiber 652 G non-linear effects do not appear in the 1550 nm window as the number of channels remains less than or equal to 32 channels and the power per channel remains below 1 mw.

Different techniques used to correct these phenomena: the case of the DCF (Dispersion Compensating Fiber) which is to introduce in the binding section of fiber producing a negative dispersion (around -100 ps / nm.km) compensation.

However, the technologies and DWDM DWDM-U have not yet reached their limits.

New techniques under development will further increase the capacity of optical systems:
- Soliton transmission allowing the transport of very narrow pulses over thousands of km without distortion, while maintaining a broad bandwidth;
- Pulse modulation, or duo-binary transmission, allowing the multiplication by two or three times the flow-mail, using pulse 2 or 3 levels binaries;
- Amplification and multiplexing in the 1300 nm window to improve returns on conventional optical fibers G652 experiencing limitations in the use of DWDM systems at 1550 nm.


In addition, devices such as multiplexers to insertion / extrat optics (Optical Add Drop Multiplexing: OADM) Reconfigurable:

brewers and optical (Optical Cross-Connect: OXC)

give operators flexibility to optimize their networks, primarily long-haul networks. Indeed, the price of these technologies can not be used on networks of local loops, where it should be more equipment. They particularly need to use cooled lasers. Therefore, it has grown quite recently another less expensive technology called CWDM (Coarse WDM) which saves about 30% over a DWDM system.

Antennas recycled

Near the village of Takahagi, Japan, two giant antennae installed in the early 1960s as part of the creation of the first Japanese telecommunications network, have a second life ... as observatories radio astronomy.

An unexpected partnership between a university and a village in 2007, it turned out when he learned that the telecommunications company converted to fiber optics, to close the two antennas. They found allies in Ibaraki University, who saw an opportunity to join an international network of observation of the cosmos, the Very Long Baseline Interferometry,

According to Science, this is not even the first time an old telecom antenna is "recycled" for radio-astronomy, and it will not be the last, as fiber optics spread throughout the world, edging out satellite communications.

Sunday, August 9, 2009

The applications of optical fiber

Today, work stations are interconnected using network using fiber optics as its use allows for information flows faster and greater security in transmissions.
In telephony, coaxial cables are slowly replaced by fiber optiques.en Indeed, it is more economical on long and short distances and the number of components required is less important.
Its use is particularly interesting for the military because it gives them some advantages:
low-weight
-size of the fiber
-insensitivity to interference and detection



FIBER OPTICS

1.-The cable technique
The optical fiber was used for these connections, because of relatively long distances, its weakening low prevents the installation of repeaters, unlike coaxial and microwave links that were not interactive. France Telecom is responsible for receiving the programs and then transmits to the control of the operator. They are then sent via fiber to the center of France Telecom supervision and then to the distribution centers.
The first urban fiber network in 1980 in Paris, between two central electronic. The first series of orders were placed in 1982 and the beginning of the massive achievements in 1983. Since 1987 has used the new fiber. Currently three quarters of the fibers are installed in the Paris area . It operate without repeater to 34 Mbits / s. End 1988 150000 Km fiber was employed and 300 000 km ordered.
Approximately 200 000 km of fiber will be laid in intercity by 10 years.

The strategy of the Directorate General of national networks is as follows:

* Skip to the fiber axis for all major risk of saturation in the short and medium term.
* Search the optical connection.
* Aim for optical services in large cities.


2.-Areas of advanced telecommunications (ZTA)

Service very efficient telecommunications are available to offer to businesses: optical fiber networks connected to ISDN 2nd generation, possible reasons for the Telecom 1 satellites and IBS to American and European cities.

3 .- Vidéodyn
The name brings together all the resources available to either customers or subscribers for the occasional television transmissions. Urban networks used for routing fiber optic part in the big cities: they provide connections between telephone exchanges and fuel distribution centers neighborhoods. In addition to the images for the general public, these materials are capable of delivering on fiber, high-speed signals to broadband can be used to establish permanent or temporary connections between different devices.

4 .- The broadband ISDN
ISDN is based on a completely digital and optical. Digital satellite hubs connect analog phones and digital switches to digital. ISDN is established since 1987 in the northern coast. It is now in Paris and throughout France. The standard digital connections adapted to the volume of communication of each user for the transportation of voice, fax, videotex and the data twice 64kbit / s a single cable. The services on fiber optic networks to broadband therefore complement those of the first generation narrowband: banks allow multimedia video, downloading videos or software.

5 .- The domotics
Centralized technical management of a smart building can include fire, floods, gas leaks, alerting services, remote etc ... This requires a "home bus" based on fiber optics.

network type (example)

Saturday, August 8, 2009

The option put forward by Free multifibre is validated by ARCEP in France

About the future deployment of fiber optics in France, the regulatory authority for telecommunications (ARCEP) has taken a position on two key points. The first concerns the choice of technology FFTH (abandoned by most developed countries), which brings fiber to the subscriber's home. In its communiqué ARCEP said "the dynamics of the broadband market in France fixed and palatability of the operators in this market to invest in a new local loop fiber to the subscriber (FTTH) is a unique in Europe, particularly conducive to the development of high speed in the territory. "

The second point talks about the choice of options and monofibre multifibre defended by Orange and Free. In his opinion, the authority goes against the assertion of Orange, who judges the option multifibre too expensive, and formally introduced it in the opportunities available in each building so that this solution is installed each When an operator wishes.

The telecoms watchdog said that in the 148 municipalities, or 5.16 million homes, "any operator may request the operator of a building (ie the operator chosen by the co-ownership fibrer building) to have a dedicated fiber for each additional housing, with a pre-installation and co-financing of initial investment. "

The authority says both that this is "conducive to the dynamics of competition and (offer) a guarantee for the future without creating undue hardship for the operators" and that its additional cost is modest compared to monofibre architecture and encourages investment in the fiber properties, encouraging a sharing of costs and hence risk.

Finally for ARCEP 'point of view, the laying of fiber Supernumeraries can change more easily operator (without loss of service) and subscribe to services from different operators.

Wednesday, August 5, 2009

Transmission systems over optical fiber

Compared to other existing transmission media, fiber has a nearly constant attenuation over a large frequency range (several thousands of gigahertz) and offers the advantage of huge bandwidth, for now consider the transmission of digital flow very large (several terabit / second) required by the multiplication of services and the increased need for transmission of images. Very fast too, it is apparent that the optical system, compared to coaxial cable systems of equivalent capacity, a significant gain on the distance between repeaters-regenerators, passing a few kilometers to several tens of kilometers. From 1978 installed systems were working at the optical wavelength of 0.8 m, delivering a throughput of between 50 and 100 Mbit / s with repeater spacing of 10 km, ie approximately three times more than coaxial cable systems of equivalent capacity.

The second generation of transmission systems over optical fiber, which emerged in the 1980s, follows directly from the development of single mode fiber and semiconductor laser at 1.3 m, wavelength for which the chromatic dispersion (ie the distortion on the signals induced by the spread) is minimal. Data rates exceeding 1 Gbit / s with repeater spacing of several tens of kilometers, are met. The scope of these systems are limited by the losses of the fiber, 0.5 dB / km at best, and the idea appears to develop sources emitting at a wavelength of 1.55 m for which l mitigation is minimal. However, this gain is destroyed by the effect of chromatic dispersion, all wavelengths can not propagate at the same speed. The chromatic dispersion of the material of the fiber is much higher than 1.3 m and it is that comes when the limitation of bandwidth and therefore the flow. Simultaneous progress on both the lasers emitting a single mode on the medium of transmission (dispersion shifted fiber) will bring solutions to these problems and the first systems working at 1.55 m appear in the late 1980s, with a throughput greater than 2 Gbit / s.

Emerged in the late 1980s and became very rapid industrial products, fiber amplifiers will bring a revolution in the field of optical fiber communications: inserted into the transmission line, they can compensate for the attenuation of the fiber and thus increase the range of transmission systems, at the cost of added noise. Used as preamplifiers, they increase the sensitivity of optical receivers. Finally, their huge bandwidth (30 nm and even more today) allows consideration of the amplification of multiple optical carriers in the spectrum juxtaposed, forming what is called a multiplex. Thus was born the concept of multiplexing wavelength (WDM Wavelength Division Multiplexing), each fiber carrying a multiplex of N channels is equivalent in capacity to N fibers each carrying a channel, and it is easily conceivable that this approach can potentially d increase the capacity of a network of very large without changing its physical infrastructure. Systems using this technique, mostly with a flow rate of 2.5 Gbit / s per channel, are now being installed in all major global players in their transport networks to cope with traffic growth expected in the coming years. Systems with N × 10 Gbit / s are offered by manufacturers and installed and the shift to multiplex large numbers of channels and (or) high capacity per channel will likely continue in the coming years, to address the need for capacity growth experienced by transport networks such as metropolitan networks.

Finally, the optical transmission can now achieve a quality (in terms of error rates) much higher than earlier systems, particularly microwave.

The optical fiber is also used in video communications networks to transmit a multiplex of sub-carrier electric intensity modulate a carrier perspective. Each of these sub-carrier, which corresponds to a television channel, is itself so analog modulated (frequency modulation, amplitude modulation single sideband) or digital (phase modulation, amplitude modulation on two quadrature carriers ...).

Saturday, August 1, 2009

Acousto-optical modulator

The diffraction of light by an ultrasonic wave is used in the acousto-optical modulators.



The high frequency generator (F = 80 MHz) generated in the strong wave acoustic wavelength Λ = C / F where the acoustic velocity is C = 4200 m / s therefore Λ = 52.5 m. The laser beam is diffracted by the ultrasonic wave. Here we are dealing with the Bragg diffraction since the diffraction angle is such that we can not neglect the diffracting three-dimensional environment (ie in inside the crystal, the deviation of a light ray is such that it will through several periods of network noise, see below **). For a maximum intensity is diffracted in the order 1, we must direct the cell to have an angle of incidence equals the angle of Bragg:
θB = λ / 2Λ = 6.0 mrad = 0.35 °
The laser beam is then deflected a corner:
2 θB = λ / Λ = 12 mrad = 0.69 °



Network ** 2D or 3D? : There are in general two types of diffraction, following a laser beam diffracted or not returned in an adjacent layer of a thick network: In the 1st case it is Bragg diffraction (3D network) in the second case, we speak of the Raman-Nath (2D network). On moves from one regime to another for a network of thickness Ec. In the experiment described in the leaflet "Optical and acoustic,the light was diffracted by a 2D network (the frequency being much lower, the period is greater: Λ / 2 ≈ 0.7 mm
Thus Ec ≈ 1m). Here against the network period is very short short (Λ / 2 = 26 m,thus Ec ≈ 1 mm): we are here in a Bragg regime.
Measuring θB:
Adjust the orientation of the cell so as to have a maximum intensity in the order 1 (use a photodetector for further details). At a distance 245 cm from the cell, separating the two beams main (order 0 and 1) is 3.0 cm. We therefore measured
θB an angle 2 = 3.0 / 245 = 12 mrad in agreement with the value calculated above.
Measuring the effectiveness of the modulator:
In the absence of ultrasonic wave is measured by such a power P = 3.30 mW.
With the ultrasonic wave, the power measured in the order 1 is P1 = 2.40 mW.
Efficiency is therefore P1 / P = 2.40 / 3.30 = 73% (max efficiency = 85% according to the notice).

Modulation:
The amplitude of the ultrasonic wave can be modulated by an external (GBF 0-5 V connected to the "mod
input generator HF) frequency fmod (15 MHz max), which has the effect of the intensity diffracted in
Order 1. In this case, the HF generator switch must be set to "OFF" (in the "cw", the HF signal is not modulated). To demonstrate an application telecoms ", the adjustment can be made from the signal output of a radio (see montage below).




• Other applications: ACOUSTO-OPTIC DEFLECTOR:
By modulating this time not the amplitude but the frequency F of the HF signal, it changes the wavelength Ultrasonic Λ therefore the angle of diffraction. This allows to control the deflection of a laser beam by a signal electric. This effect is used in scanners for example. This experience can not be achieved with our hardware because we do not currently supply a variable frequency RF or deflector acoustooptique.
Indeed, for applications to the deflection, we use acousto-optic cells that operate on a acoustic mode of low speed of propagation, which allows for a low acoustic wavelength Λ and a wide angle of deflection (typically: C = 500 m / s therefore Λ m = 6 to F = 80 MHz and Δθ = 50 mrad at λ = 633 nm for a variation of the acoustic frequency ΔF = 40 MHz). For applications to modulation, is preferred by against using a sound speed (C = 4200 m / s) because the time between the laser beam in the
acoustic wavelength Λ, which limits the high frequency performance of the modulator, with typically 160 ns per mm laser beam to the modulator, 1μs/mm against the deflector (source: AA Optoelectronic).

Friday, July 31, 2009

OPTICAL FIBER AT HOME

The pooling of the optical fiber to the home (FTTH) explained here:

The optical fiber to the home (FTTH) is criticized for its delay and its long established. Many critics have made but few seek to understand and explain what happens. Here is an attempt to decrypt.

The optical fiber represents a significant investment, it is currently mainly for housing: buildings. The reason is quite simple: the deployment of fiber for several apartments, the costs are divided. So dense areas are targeted first by the operators. That is why the explanations that follow are based on the example of deployment for buildings and apartments. The principle of FTTH for houses is similar but the conditions are less explicit mutualisation by ARCEP and operators.

What is optical fiber to the home?

To begin a drawing which explains briefly the principle of optical fiber to the home. The scheme is explained in more detail in the following in particular about 2 types of architecture.





As you can see, the principle is quite simple: to link directly the apartment of the subscriber to the Internet via an optical fiber from the apartment to a room called NRO (Node Connection Optics ) which are all connected subscribers. The equivalent of the NRO in the current telephone infrastructure (telephone lines with a pair of copper of France Telecom) is the dispatcher or call NRA (Node Connection Subscriber). The fiber optic cable between the NRO and the home is called optical local loop (the copper telephone line is called local loop copper).

Where it becomes complicated is in the first place there are several technologies involved and there were several operators: therefore pooled investments: the work done and fiber deployed to reduce these investments (this could cover more area faster in particular).

The 2 families FTTH Technologies in the P2P FTTH PON and FTTH

There are basically two types of deployment of optical fiber to home deployments in P2P - Point to Point (Peer to Peer is in french, Peer to Peer or point to point) and deployments in PON (Passive Optical Network). With a roll-to-peer (P2P), each home has its own fiber optic up to NRO. With a deployment PON, an optical fiber from NRO and is divided into 64 fibers, 128 fibers and more fibers are connected to the homes of subscribers. The PON can be seen as a tree whose trunk is the optical fiber that is connected to the NRO and the branches are optical fibers connected the homes of subscribers. Some operators have opted for a technology rather than another and others are torn between two or believing that technology is more efficient in the city and the other more effective campaign.

The advantages and disadvantages of these 2 families technologies are the subject of endless debates. ARCEP (Autorité de Régulation des Communications Électroniques and Postcards) and the government chose not to settle for one of two technologies. As this is not the subject of these explanations, we will not go no more in this debate or in the details of these technologies.

The point is that the existence of these 2 technologies complicates sharing: share its infrastructure, it is impossible to use equipment on a P2P infrastructure PON. Against the opposite may be possible: it may well make the PON with a P2P infrastructure, the "cutting" is the level of NRO. It may very well be against sharing infrastructure point to point with another operator wants to point to point, this is addressed in a second time.

Comment on mutualisms then?

All is not lost! You can still share a good part of the investments necessary for the deployment of fiber optics. To switch from fiber to the home, it is NRO and it is up to the apartment. There are not many solutions: sewers (only in some large cities), the sheaths of France Telecom last few months and if you have to "open up" the streets to ask new fork. It is sometimes necessary.

Sharing fork

Small rapid definition of a sheath is a tube or a sleeve where you can get coaxial cables (used for example by Numericable), electric cables, telephone or fiber optics.

Regarding the fork of France Télécom, he currently serves in particular to bring the telephone lines into the home. In recent months, following the demand for Free and ARCEP, France Telecom provides operators offering fork which came into effect shortly. It allows alternative operators to use the existing fork from France Telecom for deployment of fiber to the home. France Telecom already used them before, and the alternative operators (Free & SFR) have used so far mainly sewers (only in some large cities) for deployment of fiber optics. France Telecom is the main operator holding a fork with Numericable to a lesser extent.

This sharing sheaths can be realized over the entire horizontal part of the deployment. The horizontal part means the part between the NRO and the foot of building. On this part of the fiber optic infrastructure may be different (P2P or PON), they can not be shared if they are of different types. Thus the fiber optic deployment is not shared on this part for operators deploying infrastructure types.

After a somewhat difficult start sharing fork by the incumbent operators others have recently noted the effective implementation of the reference offer of France Telecom on access to its fork. Mutualization is en route to this part of the deployments and ARCEP will continue to monitor developments in this offer and the conditions for its implementation.

Mutualisation of fiber on the horizontal part of the same type of infrastructure

As against, for operators wishing to make a deployment point to point (P2P), they can share their infrastructure, it is sufficient that the operator wants to use optical fibers already deployed its equipment installed in the NRO (or near). For example, the supply of mutualisation Free provides an offer of resale in NRO (in addition to sharing in building up).

Only PON deployments in the current state of things (this change may be in the future with shared wavelength discussed at the end of the article) do not allow sharing at the physical level of fiber deployed until 'length of building.

Pooling in the building: the end

If you look at a diagram of PON deployment, we can see that in the building (the part that is called back end of deployment), there is an optical fiber necessary per flat, like a P2P deployment. Finally! We can share the deployment in the building! Thus an operator is deploying optical fiber in each apartment building until the foot and the other operators can directly connect the foot of building.

During discussions between operators and ARCEP, Free has proposed a solution mutualisation in buildings: the multifibre. At first glance the solution and is amazing when you thought you just said that it may be a good solution.

What is Multi?

Caution: Because of the complexity of the topic, it is possible to believe that the Multifibre corresponds to a deployment and that the P2P monofibre corresponds to a PON deployment or it is not. The monofibre applies equally in both PON and P2P in the multifibre applies P2P that PON.

The Multifibre to exist between the foot of the building as the apartment and fibers to each subscriber that there are operators. Here, at first sight is astonishing: there is more sharing on the back end. One wonders then what it really is apart from increasing the cost of deployment at the end. Just imagine the life of the optical fiber over several decades beginning with the deployment and how many operators will be arriving in foot building.

On the number of operators arriving foot building is fairly simple to calculate if a point to point operator is already present in a building, another trader wishing to deploy point to point does not have much interest redeployed to go until the fiber foot building, it can connect directly to the NRO. As against an operator who deploys type PON infrastructure must go to building up and other operators may PON pool at the logical level (see below) with this operator since it is the solution generally adopted by pooling operators currently PON. This is an operator and an operator P2P PON foot building, or 2 operators and 2 fiber per apartment. Investments to go down the building is substantial and the number of buildings is also a result, one should not see 2 operators per building (may be in Paris and in some very dense).



This photo shows a box with 2 fiber fiber (below), so an installation multifibre

So when deploying fiber in the building, the operator raises 2 fibers per apartment, it connects to one of the two and the day when another operator arrives, it is sufficient to connect at the bottom of property to the remaining fiber for each apartment. It therefore does not require that a final foot building where an operator comes up building. No intervention (except for possible interventions SAV) will be required to foot building. Only the wiring is necessary to NRO and the connection to the proper perspective in the apartment of the subscriber (the subscriber can do with a box with 2 outlets), just as with the telephone lines currently, when you order ADSL, it is necessary that France Telecom makes a connection to the NRA.




This photo shows the components of a FTTH (Multi) with the subscriber box located in the flat (top left photo), fibers that descend into the riser of the building (right), and Finally enclosures operators (which is building up), 1 for each operator, each of 2 fibers from an apartment is connected to one of these boxes.

To further compare with the existing telephone lines, if you look at your phone box, you can see on your phone you have pairs of brass and more (even surplus). And this is reflected on the different parts of your telephone line leading to the telephone dispatcher. This allows for multiple phone lines (with couplers mother) or to use another pair of copper if a pair is faulty.

As against the single-fiber, whenever the subscriber changes its physical operator (operator at the foot of building), the intervention of a technician at the bottom of the building is necessary.

Now, if you have the settings, you can make a small calculation:

cost of installation monofibre (1 fiber between the apartment and the building up) + cost interventions technicians building up over tens of years (the local loop fiber is supposed to last) = total cost single fiber
cost of installation multifibre (2 fibers between the apartment and the building up) = total cost multifibre

Saturday, July 25, 2009

Optical or coaxial, what to choose? :

In the "entry level", ie in very affordable prices, an optical cable has a good chance to be more effective because it is insensitive to electromagnetic interference, in fact the optical link uses the light, however, this process requires more than an RCA coaxial connection, adding a digital converter / optical output of dvd player (internal), a converter and optical / digital input of the amplifier (internal) and these converters have a maximum speed of 6Mhz (minimum) for most, which is sufficient for digital sound samples 48kHz (ie a DVD classic) but enough for a sampling of 96 or 192 kHz (DVD -audio, HD-DVD ...) and sometimes poor quality of these converters can result in distortions of the digital signal containing the flow of DTS or Dolby Digital.
Also note that for a long link (over 10m), it is preferable to use a coaxial connection for the power of light (Toslink transmitter) in this case is too small for larger lengths.

The advantages of the optical link:
- Insensitive to electromagnetic waves
- No transfer of masses (galvanic isolation with opto-electronic elements)
- An optical cable quality is significantly less expensive than coaxial cable RCA quality.

The disadvantages of the optical link:
- Sensitive to dust
- Significant loss factor (hence our advice to limit this type of cable to a length of 10m max)
- Speed limited
- Double conversion necessary
- Somewhat fragile
- Connectors Optical often of poor quality equipment on the entry.

With an RCA coaxial shielded cable of very good quality (OFC copper conductors, Gold plated connectors ...), there is a good chance that the sound quality is better because in this case it does not convert the signal twice, and therefore there is no limitation in speed 6Mhz minimum

The advantages of coaxial RCA connection:

- Flow rate well above the optical link:> 100 Mhz, therefore compatible with high sampling rate (192kHz).
- No galvanic isolation between the player and the amp, so there may be mass transfers.
- Attenuation of signal rather low (around 3 to 30 dB per km).

The disadvantages of the RCA coaxial connection:
- Bounces waves for cables longer than 15m when the connector impedance is 50 Ohms (often the case) instead 75 Ohms.
- Cable quality expensive.

In conclusion?

The optical link is theoretically superior to the coaxial connection but the optical connectors are often of very poor quality, and throughput is limited by the digital / optical and optical / digital coaxial cable can achieve better results in the vast majority of cases, including links lengths over 10m.

Among the best brands of RCA coaxial cables can include Cable Positive (Optimum Libra), QED (QUNEX series), or Audioquest.

Wednesday, July 22, 2009

How the information is transmitted through a fiber optic cable?

Whatever type of cable is used, information is transmitted in the same way. Because the interior of the fiber optic cable is coated with a reflection, total internal reflection is present in the fiber optics. In order to provide information within the fiber optic, analog information must first be converted into digital signals. Once this information is converted, lasers can transmit digital signals in the form of pulses of light.
Because there is total internal reflection within the fiber optics, information that is transmitted in the form of light is able to constantly bounce off the reflective surfaces of the fiber. This is important because even when the fiber optic cable is defined by an area which requires that bend or twist, the total internal reflection allows the light to continue traveling through the cable to its final destination.

Tuesday, July 21, 2009

Types of fiber optic cable

There are two main types of fiber optic cable, which are single mode and multi-mode.


Single mode: Single mode fiber is a small component that has only one mode of transmission. Single mode fiber is able to transmit at high speeds over long distances because of their small base. Because only mode fiber optic cable allows for transmission distances longer and faster than the rate of transmission of multi-mode fiber, it costs more fibers that are multi-mode.

Multi-mode: The reason that multi-mode has a lower single-mode because it has a large diameter. As a result of the larger diameter, multi-mode is capable of generating broadband high speed when it moves to the amounts of medium distances. However, in long distances, the large diameter can cause problems because the multiple paths of light can cause different types of distortion.

Sunday, July 19, 2009

FIBER OPTICAL WIRE COMMUNICATION

The discovery of the laser in 1960 has provided light sources suitable for the transmission and processing of information. Optical transmission has several advantages over radio transmission: speed (of light), high speed and a wider carrier frequency. It had one drawback: its price, but it becomes less and less true.


Operation of fiber: the preform (Bar glass 2 indices) is heated in a furnace, and stretched continuously by a cylinder which wraps around the fiber. Along the way, various systems adjust the speed of stretch and the oven temperature as a function of fiber diameter, measured by laser.



From 1960 to 1975, researchers, especially American, have worked to find a low attenuation. The single crystals, first approached, were abandoned in favor of glass, transparent material par excellence. The manufacturing techniques of fiber glass, and especially the research of high purity, were not without mentioning the manufacturing process of semiconductors. Therefore CNET (1) Lannion B, with his experience in semiconductors, decided to embark on the epic fiber.


20 Years of Progress

By applying the method to fibers called MCVD (Modified Chemical Vapor Deposition), obtained by CNET in 1975 silica fiber whose heart is enriched in germanium. The variation index between the glass heart and the sheath allows a reduced signal in the order of 5 decibels (2) per km for a laser wavelength of 0.85 m. Gradually improve the performance: in 80 years, the multimode beam, due to interference limitations, is replaced by a single. Currently, with a fiber laser and a 1.3 m or 1.5 m, the loss of signal strength is only 0.3 to 2 db / km, the wavelength chosen. This choice is based on the target application: for short distances at high speed information, use 1.3 m, where chromatic dispersion is the lowest, at the expense of a slightly more attenuation important. The other option is usually considered for international routes and especially the submarine links.


-> Booting the fiber.


A problem of connectivity

After some distance, the signal is very attenuated force: it has to be regenerated. So far, a device called a repeater transforming the optical signal into an electrical signal and amplify it back before the optical form. For the transatlantic TAT9, immerse it took a repeater every 50 km. A new system is currently under development: the optical amplifier. A laser is coupled to the fiber line, the signal passes through a fiber amplifier before reaching the fiber line. This system, returning a signal more faithfully than does the repeater, will link more than 500 km without connections.


The challenge of CNET

Optical fibers are material costs: about 1.20 francs per meter compared to 30 cents for copper. This hampers the development of optical transmission, despite its high speed performance and speed. To stand up to major Japanese and American, CNET strives to reduce production costs. Target: the fiber optic 40 cents per meter. For that, he worked closely with the company of Cables de Lyon. Stay tuned!



NOTES:

(1) CNET: Center National d'Etudes des Telecommunications.
(2) db = decibel is the optical equivalent decibel acoustics. It represents the signal attenuation, proportional to the ratio of the logarithmic power on the power recovered.

Friday, July 17, 2009

STEPS FOR INSTALLATION

It happens quite often to meet with individuals to install their own communications network in their house or apartment at rehabilitation or even when a building to which they are largely hand.

It is not so difficult to get started ... still need a few basics and roll their sleeves up.

The installation will take place in stages:

The VDI cables:

In a communication network, the infrastructure is designed in a star. That is to say that there is a cable that part of the table for each of the RJ45 sockets distributed throughout the dwelling. Thus there are so many cables that catch. The Voice Data Images cables are twisted pair cables covered most of the time one or more aluminum screens, all in a PVC sheath. Please allow for these cables in conduit diameter 20 mm or 22. Although measuring routes considering the appropriate passages (on average 15 to 20 m per connection in a home). Standardization ensures connections up to 50 m maximum. The cables should be marked and numbered at each end of the cable.

The installation of the table of communication:

Table of communication will be mounting against a wall or recessed in a form known as GTL (shafts Housing) where we find the electrical panel and platinum in particular EDF. It will bring to the table all the multimedia resources such as the arrival of the telephone line and internet, TV antenna, the access control system for example ... Each of these "resources" will own equipment to to connect and distribute on RJ45 sockets distribution. For example, a DTI and QFM for telephony and Internet, TV or Distributor coaxial splitter for the antenna .

The connection of RJ45 outlets communication:

We Connect the RJ45 communication on both sides of a connection, one at the table and the other in one of the housing. The RJ45 sockets to connect using a cable convention specific and standardized at the international level: EIA TIA 568 B. Just follow the instructions carefully when connecting the color codes are fundamental. It is imperative to have numbered each take in order to navigate and not waste time.

Commissioning:

The installation and validation, it should choose the place of its multimedia equipment in the house and connected by cords brewing facing each resource involved. Compliance with a color-coded by type of resource will allow for better visual reading of the installation in the table (red cords for the TV, computer blue, ivory for telephony, for its black, yellow for the doorman , green for other functions ...) The company provides Casanova, for the most courageous, a help in the design and costing and sales training free.

Thursday, July 16, 2009

Conditions of installation of the Fiber Optics.

Decrees 2009-52 and 2009-54 for implementing the LME (Law of Modernization of the Economy) establish the conditions for installing the fiber optics.

Here are some selections not so trivial as this:

"Buildings must be equipped with electronic communication lines at very high speed optical fiber serving each dwelling. These lines connect each dwelling with at least one fiber per unit at a connection point in the building, accessible and providing access to several electronic communication networks. (...) Each dwelling is equipped with indoor installation such as to enable the service to each of the major "


Fiber optics will be the support of several networks such as television, telephony and the Internet by example and lead to an array of communication for dissemination of these services (high speed) throughout the house.
"Installation, maintenance, replacement and management where appropriate lines are at the expense of the operator signatory to the Convention. (...) The agreement authorizes the use by other operators of reception facilities for electronic communication lines installed by the signatory operator. "


The building will have an owner operator of the facility, signed an agreement with the landlord or the condominium, but the network should be shared open to other operators.


"The signatory operator serves the housing (...) by a continuous path from the optical fiber connection point and leading to a termination device installed within each dwelling. (...) The operator complies with the rules of the building, as well as standards and rules. "
The operator will make at its expense the work of building riser must respect the norms and rules of the art wiring. Fiber optics will reach an array of communication (brassable) and multimedia services are distributed within the housing by a star-wiring and sockets RJ45 communication.

Monday, July 13, 2009

Advantages of fiber optics over Copper

The optical fiber has advantages in compared to copper:
- The spread signal undergoes low relief and has no need to be frequently reamplified;
- You can perform data transmission to very high speeds (currently up to 160 Gbit/s laboratory);
- The signals are insensitive to electromagnetic perturbations ;
- It is possible to multiplex several spectrally data types on a single fiber, it transmits multiple channels, each with its own "Color" (or wavelength, or "lambda");
- The optical fiber cables are easier to handle, they can stand ups are important and lighter and more flexible than copper

Optical technology

Optical transmission technology which made its appearance in 70 years, spread over a
ten years in the networks represented in the form of optical fibers. In 2004, 55million km of fiber have been made by operators in the world, and this phenomenon continues each year. That is why there is an increased supply fiber Optical black at the expense of leased lines in most part of Europe. Optical technologies haveemerged through their capacity to carry data at high speed, their flexibility allocation of resources and the simplicity of their interfaces by over SDH technology (Synchronous Digital Hierarchy).






A dedicated fiber optic communications for long distance is a "bar" very fine (125 m) glass extremely pure, which gives the property to behave as a guide light on several hundreds of kilometers. Fiber, wrapped in a layer of plastic, is consisting of a core and a sheath of glass, of clues different environment. A phenomenon
total internal reflection allows the light to spread along the core of the fiber.


Sunday, July 12, 2009

WDM technology

The majority of optical networks are currently based on spectral multiplexing WDM
(Wavelength Division Multiplexing), is injected in a same fiber signals dedicated to several applicationsor different users and it performs a correspondence between the colors of beams light and interfaces Client ends
optical links.
Each node in the network, it has the possibility to extract or insert at channel of choice.
Recommendations of the ITU (International Telecommunications) define very precisely the characteristics of channels to use, including their central wavelength and width of each beam.

Two main types of WDM exist:
- The CWDM (Coarse WDM) is used to multiplex simple and inexpensive way to eighteen
lambdas on access networks, or metropolitan on a spectrum ranging from 1270 to 1610 nm.
The spacing between each lambda is important (20 nm), the temperature of each laser is not controlled and the wavelengths plants can therefore suffer no significant deviations from about 6 or 7 nm.
The scope of such a system has limited the lack of function of re-amplification, 80 km at most.
- The DWDM (Dense WDM) is a solution to transport of several dozen high lambdas
flow over long distances, the spacing between lambdas can vary from 1.6 nm (200 GHz) to 0.1 nm (12.5 GHz).
An enslavement of laser temperature necessary to avoid any deviation of the lengths
wave.
The use of electronics and photonics accuracy that results justify the cost differences between CWDM and DWDM.

The DWDM channels are located on the C and L bands, it is known technically amplifier, distances transmission can reach several thousand km.

Saturday, July 11, 2009

Conference OFC / NFOEC 2008

Conference OFC / NFOEC 2008, which focuses on optical communications (Optical Fiber Communication / National Fiber Optic Engineers Conference), held in San Diego, California at the end of February. This annual conference focuses on current U.S. transportation optical telecommunications, a sector which is highly holder, with the explosion of multimedia content on the Internet. Each year this conference is becoming increasingly international. In fact, traffic on the Internet constantly double every 16 months: daily trade in 9000 reaching peta-bytes (9 billion gigabytes) and should reach 21 000 peta-bytes in 2012.
The major theme of discussion in the previous edition focused on the adoption of 40Gigabit / s (Gbps), and in particular whether it should not work directly on the next generation (100Gbit / s). This year, the 40Gbit / s and 100Gbit / s have been assimilated into the same category and, despite the relatively slow for these components, they have been a major focus of this conference. The market for components for ultra high speed is estimated at $ 900 million for the year 2012, representing 10% of components for optical telecommunications.
Thus, many components to 40Gbit / s were presented at the exhibition (of high power lasers to modulators and demodulators via fleas specific treatments), and showed that the technology was mature and treated. Moreover, these transfers are already used in some deployments of FTTH (Fiber To The Home).
Another very popular technology on the show was the SFP + technology for new optical connectors. Smaller than its competitors and more recently standardized, this technology can increase the number of optical ports and card supports the new standards and 10Gbit / s in contrast to his predecessor (SFP).
Since the technology 40Gbit / s are developed, the main discussions focused on the development of technologies 100Gbit / s and beyond, and the specification of standards along with these innovations.
The conference was also a scientific meeting, several research papers were presented during those few days. So Alcatel-Lucent and its group of Bell Labs research showed how they had managed to develop a transmission reaches record 16.4 Terabit / s (16 400 Gbit / s), over 2 550 km using 164 channels to 100Gbit / s multiplexed and this sets a new speed record.
This demonstration, along with three other articles on Bell Labs circuits transmissions 100Gbit / s (on a receiver on a bipolar modulator and another modulator) showed that this new technology and Ethernet 100Gbit / s approaching commercialization.
This market is still developing and has gone bearer for the coming years with new innovations.

Multiplexing, modulation WDM, DWDM

In any transmission, it is interesting to move at the same time in the same conductor (here a single fiber) up communications companies, neither of which comes another scramble. They are therefore each carries a different wavelength is multiplexing.
Multiplexing and its inverse are given by Mux / Demux. The different wavelengths are generally assembled and separated by means of optical filters such as thin films (the most commonly prevalent).
A bit like on a combined technology "common rail" a new generation of diesel engines more efficient, combining the different modulation types for different types of fiber optic transmission, and it is possible to choose a type of modulation for the same material, or need to know the physical principle to use in the SI.

For information, here are some words:

WDM (Wavelength Division Multiplexing) (G.692): several trains of digital signals at the same speed of modulation, but each to a separate wavelength.

DWDM (Dense Wavelength Division Multiplexing) technology is known as dense WDM spacing when used between two wavelengths is equal to or less than 100 GHz. It works now for long-distance transmissions. In practice, this means that we put in a lot of fiber signals carried by frequencies very close to each other.

U-DWDM (Ultra - Dense Wavelength Division Multiplexing) allows up to 400 channels.

CWDM (Coarse Wavelength Division Multiplexing) only 8 to 16 channels, but a less expensive technology used in particular for local loops (MAN).

Protocols

Protocols transmitted over fiber optics include:

SONET / SDH
ATM
Ethernet,
ESCON,
FICON,
Fiber Channel.


CWDM
DWDM technology has relatively high costs.
• high performance fiber
• cooled lasers
• fine wavelengths very close to each other.

Technology CWDM (Coarse Wavelength Division Multiplexing) is a WDM economy. The channels are removed (coarse). In fact, according to its quality, we only have 8 or 16 channels per fiber. The material used, a moderate cost and use without constraints, allows for installation in the equipment end (local loops, business).

Advantages of fiber optics

The interest of this method of transmission through optical fiber, a priori exotic, are numerous:
signal loss over long distances much smaller than in an electric conductor in a metal
transmission speeds very high,
low weight per meter (this is important, both to reduce the weight exerted the complex installations in buildings to reduce the traction of long cables at their ends),
insensitivity to external interference (near a neon or a high-voltage cable, for example)
no heating (high frequency copper boiler, it must be cool to get high data rates).
A case of mode
Optical mode is the number of paths (for simplicity).
In a multimode fiber, light can take many paths (see diagram). In a fiber, it is trapped in a direct way. It retains speed and consistency. The fiber is a fiber better than multimode fiber, but requires the use of light sources (laser) very powerful.




Multimode fiber

Multimode fiber, or MMF (MultiMode Fiber) is mainly used in local area networks (a few hundred meters). Its diameter is relatively large (50 to 85 microns). It uses an LED to generate the signal.
The establishment of this type of transmission poses few problems and does not require expensive equipment or complex to implement.
We distinguish fibers low or step index (flow rate limited to 50 Mb / s) and fiber graded index (flow rate limited to 1 Gb / s).
See the file "Fiber optic local area network."
Singlemode optical fiber
The fiber or SMF (Single Mode Fiber) is used for metropolitan networks or long-distance operators. His heart is extremely thin (a few microns). The data transmission is ensured by lasers emitting wavelengths from 1300 to 1550 nanometers and optical amplifiers at regular intervals.
We can distinguish several categories of more efficient, both in speed that distance:
• G.652 - fiber dispersion shifted not the most common. It enables transmission to 2.5 Gbps maximum.
• G.653 - dispersion shifted fiber: for submarine cables.
• G.655 - fiber to non-zero dispersion (NZDF: Non Zero Dispersion Fiber): designed for applications such as WDM (Wavelength Division Multiplexing) amplified (see below).
• G.692 - more recent, it is compatible with DWDM multiplexing. It helps to support the high speeds over distances of 600 to 2000 km (submarine cables).
It should be noted that over the distance is, the less the flow may be high.

Principle of fiber optics

Overall, fiber is composed of :

Over a glass of very fine, the heart (a few microns), a single, sometimes very long (up to several hundreds of km)
a sheath that traps light in the heart reflecting virtually without loss (generally, a transparent envelope of a refractive index lower (some will remember their physics courses),
a protective sheath that can meet several tens to several hundreds of fibers,
a system of very specific connection (if not exposed to the light ends and not out).
The lifetime of such a driver is estimated to be at least 20 years.
The electrical signal to be transmitted, originally led by drivers metal is transformed into light signal with a transceiver. The transceiver uses an LED (Light Emitting Diode - Light Emitting Diode) or a laser to produce light.
For the reverse, to convert the light signal into an electrical signal, using a detector. Usually a photodiode.