Monthly Archives: July 2013

How To Use Magnifier Inspect Fiber Optic Connector

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We can use magnifier to check the fiber optic connector pin end, which quickly determined that the connector insertion loss is high or low, the need for re-grinding. With this method, you only need a few seconds, you can initially conclude that the connector meets the quality requirements. Than the use of instruments that measure the specific optical connector insertion loss value, and then determine wheter the quality meets the requirements, greatly reducing the time and improve efficiency.

Testing Equipment

Using fiber magnifier to check fiber optic connector pins end, we need at least the following equipment:

1. 200 times or 400 times of fiber optic magnifier(according to the type of fiber connector to check the selection of suitable fiber adapters);

2. Pure alcohole and lens paper (hairless soft paper);

3. Light source (we used here instead of incandescent bulbs);

Testing Steps

Check the following steps:

1. Remove the dust cap at the end of the connector to check;
2. Insert the connector in the magnifying glass of the adapter;
3. If you can not see the field of vision magnifier pin end, then adjust the position of magnifier adjustment knob until the pin end graphics all entered the field of vision;
4. Adjust the focal length of the magnifying glass to the right position, making the pin end graphics to clear;
5. Check the pin end, works well for grinding connector. Its face should be round, very smooth, the end of the fiber core is flush with the pin, and showed concentric ring shape; If there is dust (or defects), use lens paper (hairless soft paper) stick of pure alcohol wipe until the surface no dust (or you can see the clear flaws);
6. The other end of the connector to remove the dust cap, and make the end of the pins on the incandescent bulbs, we just checked in the connector end can see the light, otherwise the connector where a fiber optic cable has broken;
7. Repeat the above steps, check again, you will see a very bright core pin end view may find minor flaws;
8. Exchange ends of the connector, repeat the above steps to check the other end;
9. Mark the connector end of the existing problems with the tag, using appropriate methods, or grinding or re-assembled connector, and then repeat the steps above to be checked.

Analysis of test results

The use of a magnifier fiber optic connector for the inspection, we can see that a very good grinding effect fiber connector pin end face should have graphical features, it can have a variety of different types of defects that the end face of the connector graphical features. According to what we see different kinds of graphics, combined with our analysis, we can take the appropriate measures for improvement, in order to ensure the quality of the connector.

Recommended to use at least 200 times (preferably 400 times) of the optical magnifier to be checked. In order to check the accuracy, certainly with and without the use of incandescent bulbs in both cases with a magnifier to check connector end. In both cases the control of the end face of the pattern that can better determine whether defective.

For a good grinding effect connectors, we do not need any additional processing, instrumentatioin can be used directly for subsequent testing. If the connector is more obvious defects (based on experience needed to judge), its loss is likely higher, beyond the acceptable range of technical requipments, we can directly determine the quality problems. But for smaller connectors defective, the loss may be within the required range, then we need to use instrumentation to determine the actual test.

How to determine whether the effect of the connector polishing is “Good”?

If the connector pin end and core are round, smooth, while the fiber core is flush with the pin end, concentricity good, it is “good”, and without blemish.

If one connector looks “bad”, then the center or not circular, or is not smooth, or concentricity deviation is large, or the presence of other defects. For example, if the fiber has partially broken, then its will not be a full circle core.

The most serious situation is that we are under a magnifier to see the clear outline of the core of the phenomenon we call “fragmentation”. More than a brief introduction to how to determine a connector is a “good” or “bad”.

Application of Optical Add-Drop Multiplexer

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What’s the Optical Add-drop Multiplexer?

An optical add-drop multiplexer (OADM) is a device used in wavelength-division multiplexing systems for multiplexing and routing different channels of light into or out of a single mode fiber (SMF). This is a type of optical node, which is generally used for the construction of optical telecommunications networks. An OADM may be considered to be a specific type of optical cross-connect.

A traditional OADM consists of three stages: an optical demultiplexer, and optical fiber multiplexer, and between them a method of reconfiguring the paths between the optical demultiplexer, the optical multiplexer and a set of ports for adding and dropping signals. The optical demultiplexer separates wavelengths in an input fiber onto ports. The reconfiguration can be achieved by a fiber patch panel or by optical switches which direct the wavelengths to the optical multiplexer or to drop ports. The optical multiplexer multiplexes the wavelength channels that are to continue on from demultiplexer ports with those from the add ports, onto a single output fiber.

Principles of OADM technology

General OADM node can use four port model (Figure 1) to represent, includes three basic functions: Drop required wavelength signal, Add rumored signal to other wavelengths pass through unaffected. OADM specific network process is as follows: WDM signal coming from the line contains mangy wavelength signals into OADM’s “MainInput” side, according to business required, from many wavelength signals to selectively retrieved from the end (Drop) output desired wavelength signal, relative to the end from the Add the wavelength of the input signal to be transmitted. While the other has nothing to do with the local wavelength channels directly through the OADM, and rumored signals multiplexed together, the line output from the OADM (Main Output) Output.


Figure 1 OADM basic model

OADM node technical classification

Optical drop multiplexer network technologies can be divided into two types, fixed optical drop multiplexer (Fixed OADM, FOADM) and reconfigurable optical drop multiplexer (Reconfigurable OADM, ROADM).

Fixed Optical Drop Multiplexer (FOADM)

FOADM to filter as the main component, and its function is fixed to join or retrieve certain light wavelengths. General common FOADM can be divided into three types, namely Thin Film Filter type (TFF type), Fiber Bragg Grating (FBG type) and integrated planar Arrayed Waveguide Gratings (AWG type).

Thin Film Filter (TFF FOADM)

* TFF FOADM using thin film between the filtering effect of the different refractive index.

Fiber Bragg Grating (FBG FOADM)

* FBG FOADM use of fiber Bragg grating filtering effect, with two circulator can become FOADM.

Arrayed Waveguide Gratings (AWG FOADM)

* AWG FOADM gererally used in semiconductor fabrication processes, the integration of different refractive index material is formed on a flat substrate in a planar waveguide, when different wavelength light source is incident through the couping after the import side, due to take a different path length, while the different phase delay caused by different wavelengths and thus produce certain wavelengths in the export side to form a constructive or destructive interference, making waves in the export side, the different wavelengths will follow the design on a different channel to reach, and thus achieve FOADM function.

Reconfigurable Optical Add/Drop Multiplexer (ROADM)

ROADM can always be adjusted with the distribution network to add and drop wavelength, which reconstruct the network resource allocation, the flexibility to meet the requires of modern urban network, so a flexible ROADM features, plus optical switch substantial advantage, making the current fastest growing ROADM based voa attenuator based ROADM (switch based OADM). ROADM mainly be the optical switch, multiplexer and demultiplexer composed, Switch-based OADM, mainly divided into Wavelength independent switch array and wavelength selection switch.


Type 1 Wavelength independent switch array

Type 2 Wavelength selective switch

All kinds of optical drop multiplexer performance comparison

OADM network applications

WDM ROADM optical fiber suitable for different network environments

OADM in the metropolitan network development tendency

1. Arbitrary choice must be retrieved, adding wavelength, the wavelength can take advantage of the limited resources, the node can be retrieved with the need to do to join the adjustment of the signal wavelength, and has a remote control functions. This can provide dynamic reconfiguration of optical communications network capable ROADM will be connected to the backbone network critical devices. And FOADM is used for wavelength demand network access will be smaller parts to reduce costs. Furthermore, ROADM use to all kinds of Tunable Laser, unable Filter, or wavelength selective optical switches and other components.

2. Must be able to convert incompatible wavelength suitable for the backbone network will be transmitted wavelengths. Therefore, OADM be combined with wavelength conversioin Transponder or other functional components.

3. Must be able to compensate for the node to make acquisistion, adding such action energy loss. Therefore, OADM optical amplifiers must be combined with functional components.

4. Wavelength signals related specifications, such as: the signal to noise ratio (S/N), the energy balance between the signal wavelength, etc., are required to meet network requirements. Therefore must be combined OADM Variable Optical Attenuator (VOA), dispersion compensation module (DCM) and other components.

Simplex And Duplex Fiber Optic Cables

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It is important to understand the different varieties of core characteristics that are available within the fiber optic cabling itself, as each of these different characteristics will have different effects on your ability to transmit information reliably. Have a look at the most common fiber optics cores used in the industry nowadays.

Simplex optical fiber Cable

Simplex means this cable is with only one thread of fiber optic glass inside the single core. And simplex cables are with one single outer jacket. Simplex fiber optic cable is used in applications that only require one-way data transfer. For instance, an interstate trucking scale that sends the weight of the truck to a monitoring station or an oil line monitor that sends data about oil flow to a central location. There are singlemode and simplex multimode fiber optic cable available. Single-mode simplex fiber optic cable is a great option for anyone setting up a cable network that will require data to travel in one direction over long distances. Since this type of cable only carries one ray of light at a time, it’s better for long-distance transmissions. Single-mode fiber itself has a high-carrying capacity, is very reliable, and has lower power consumption than other options.

Analog to digital data readouts, interstate highway sensor relays, and automated speed and boundary sensors (for sports applications) are all great uses of Simplex fiber optic cable. This form of fiber cable can be cheaper than Duplex cables, because less material is involved. Simplex cable is compatible with any HDMI extender.

Duplex Fiber Optic Cables

Duplex fiber cable can be regarded as two simplex cables, either single mode or multimode, having their jackets conjoined by a strip of jacket material, usually in a zipcord (side-by-side) style. Use duplex multimode or singlemode fiber optic cable for applications that require simultaneous, bi-directional data transfer(One fiber transmits data one direction; the other fiber transmits data in the opposite direction). Duplex fiber is available in singlemode and multimode.

Duplex Fiber Cable and Singlemode duplex cable alike are used for two-way data transfers. Larger workstations, switches, servers, and major networking hardware tends to require duplex fiber optic cable. Duplex cables can be more expensive than Simplex cables, and are compatible with any HDMI extender.

Simplex and duplex are with various cable structure types; they are different from single mode and multi mode which are related to fiber optic glass types.

Multi Fiber Cables

Both multi fiber cables and simplex cables are with a single outer jacket, but simplex only has one thread fiber glass inside the core, while multi fiber has many threads of fiber optic glass inside the core. For example, an 8-core multi fiber cable. There are ribbon type and bundle type multi fiber cables.

Single-mode fiber cables and multi-mode fiber cables are similar in many ways, with the main difference being that the glass center of single-mode cables is significantly smaller, at about 10 microns in diameter. The smaller size is what allows these cables to transmit data up to 40 miles with a bandwidth of 1Gbs.

Only need a simplex fiber cable if data will be traveling in one direction, such as with a security camera or truck weigh station. And if your data will be traveling a long distance – for instance between buildings or from one station to another – then you’re better off with a single-mode fiber cable.

How Much Do You Know About OADM

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The OADM, or optical add drop multiplexers, is a gateway into and out of a single mode fiber. In practice, most signals pass through the device, but some would be “dropped” by splitting them from the line. Signals originating at that point can be “added” into the line and directed to another destination. An OADM may be considered to be a specific type of optical cross-connect, widely used in wavelength division multiplexing systems for multiplexing and routing fiber optic signals. They selectively add and drop individual or sets of wavelength channels from a dense wavelength division multiplexing (DWDM) multi-channel stream. OADMs are used to cost effectively access part of the bandwidth in the optical domain being passed through the in-line amplifiers with the minimum amount of electronics.

OADMs have passive and active modes depending on the wavelength. In passive OADM, the add and drop wavelengths are fixed beforehand while in dynamic mode, OADM can be set to any wavelength after installation. Passive OADM uses fiber optic filters, fiber gratings, and planar waveguides in networks with WDM systems. Dynamic OADM can select any wavelength by provisioning on demand without changing its physical configuration. It is also less expensive and more flexible than passive OADM. Dynamic OADM is separated into two generations.

A typical OADM consists of three stages: an optical demultiplexer, an optical multiplexer, and between them a method of reconfiguring the paths between the optical demultiplexer, the optical multiplexer and a set of ports for adding and dropping signals. The optical demultiplexer separates wavelengths in an input fiber onto ports. The reconfiguration can be achieved by a cross connect patch panel or by optical switches which direct the wavelengths to the optical multiplexer or to drop ports. The optical multiplexer multiplexes the wavelength channels that are to continue on from demultipexer ports with those from the add ports, onto a single output fiber.

Physically, there are several ways to realize an OADM. There are a variety of demultiplexer and multiplexer technologies including thin film filters, fiber Bragg gratings with optical circulators, free space grating devices and integrated planar arrayed waveguide gratings. The switching or reconfiguration functions range from the manual fiber patch panel to a variety of switching technologies including microelectromechanical systems (MEMS), liquid crystal and thermo-optic switches in planar waveguide circuits.

CWDM and DWDM OADM provide data access for intermediate network devices along a shared optical media network path. Regardless of the network topology, OADM access points allow design flexibility to communicate to locations along the fiber path. CWDM OADM provides the ability to add or drop a single wavelength or multi-wavelengths from a fully multiplexed optical signal. This permits intermediate locations between remote sites to access the common, point-to-point fiber message linking them. Wavelengths not dropped, pass-through the OADM and keep on in the direction of the remote site. Additional selected wavelengths can be added or dropped by successive OADMS as needed.

FiberStore provides a wide selection of specialized OADMs for WDM system. Custom WDM solutions are also available for applications beyond the current product designs including mixed combinations of CWDM and DWDM.

Multimode OM4 Cable Is Available For 40G Or 100G applications

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There are different categories of graded-index multimode glass fiber cable, including OM1, OM2, OM3 and OM4 cables (OM stands for optical multi-mode). OM1 specifies 62.5-micron cable and OM2 specifies 50-micron cable. These are commonly used in premises applications for shorter reach 1Gb/s networks. But OM1 and OM2 cable are not suitable for today’s higher-speed networks. OM3 and OM4 are both laser-optimized multimode fiber (LOMMF) and were developed to accommodate faster fiber optic networking such as 10, 40, and 100 Gbps. Both are designed for use with 850-nm VCSELS (vertical-cavity surface-emitting lasers) and have aqua sheaths.

OM3 specifies an 850-nm laser-optimized 50-micron cable with an effective modal bandwidth (EMB) of 2000 MHz/km. It can support 10-Gbps link distances up to 300 meters. OM4 specifies a high-bandwidth 850-nm laser-optimized 50-micron cable an effective modal bandwidth of 4700 MHz/km. It can support 10-Gbps link distances of 550 meters. 100 Gbps distances are 100 meters and 150 meters, respectively.

What Makes OM4 Different?

OM4 fiber, with its higher bandwidth, has an extremely precise refractive index profile, virtually free of perturbations or defects. Just like OM3, OM4 is a 50-micron, considered to be laser-optimized multimode fiber for use with VCSELs. The key difference of OM4 from OM3 is in the refractive index of the fiber, which is more precisely graded to better equalize the arrival time of the light modes traveling at various speeds along the core of the fiber. Mode equalization depends on how well the graded index profile is constructed during fiber manufacturing. The better the modes are equalized, the higher the bandwidth of the fiber. This translates to higher bandwidth and a 550-meter reach for 10Gb/s (with some vendors claiming a 600-meter reach) and a 150-meter reach for 40/100 Gig, compared to 300 and 100 meters respectively for OM3.

You can use OM2 fiber with VCSELs, but its performance is limited to 550 meters at 1 Gb/s and only 82 meters at 10 Gb/s, compared to OM4 fiber’s reach of over 1000 meters at 1 Gb/s and 550 meters at 10 Gb/s.

OM3 and OM4 fibers are selected as the only multimode fiber for 40G/100G applications, which are the development trends of fiber optic communication. The 40G and 100G speeds are currently achieved by bundling multiple channels together in parallel with special multi-channel (or multi-lane) connector types. This standard defines an expected operating range of up to 100m for OM3 and up to 150m for OM4 for 40 Gigabit Ethernet and 100 Gigabit Ethernet. The OM3 and OM4 fibers are optimized for 850-nm transmission and have a minimum 2000 MHz.km and 4700 MHz.km effective modal bandwidth (EMB), respectively. Two EMB measurement techniques are used today for the bandwidth measurement. The minimum effective modal bandwidth calculated (EMBc) method, in our opinion, offers a more reliable and precise measurement compared to the differential mode delay (DMD) mask technique. With minEMBc, a true scalable bandwidth value is calculated that can reliably predict performance for different data rates and link lengths. With a connectivity solution using OM3 and OM4 fibers that have been measured using the minEMBc technique, the optical infrastructure deployed in the data center will meet the performance criteria set forth by IEEE for bandwidth.

OM4 cable is also especially well suited for shorter reach data center and high performance computing applications, which is the best option for the small percentage for users running 10Gb/s over links between 300 and 550 meters (or the even smaller percent who anticipate running 40 or 100Gb/s between 100 and 150 meters).

Benefits From LSZH Jacked Cables

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If protection of equipment or people is a design requirement, consider low-smoke zero-halogen (LSZH) jacketed cables. They emit fewer toxic fumes than standard PVC-based cable jackets. Typically, halogen free cables is used in confined spaces such as mining operations where ventilation is of concern.

What is the difference between LSZH cable and common cables?

The function and technique parameter of LSZH fiber optic cable is just like common fiber optic cables, and inner structure is also similar, the basic difference is the jackets. LSZH fiber optic jackets is more fire-resistant compared with common PVC jacketed cables, even when they are caught in fire, the burned LSZH cables provide low smoke and no halogen substances, this feature is not only environment protective but the low smoke when it got burned is also important to people and facilities in the fired place.

LSZH jacket is made up of some very special materials which are non-halogenated and flame retardant. LSZH cable jacketing is composed of thermoplastic or thermoset compounds that emit limited smoke and no halogen when exposed to high sources of heat. LSZH cable reduces the amount of harmful toxic and corrosive gas emitted during combustion. This type of material is typically used in poorly ventilated areas such as aircraft or rail cars. LSZH jackets are also safer than Plenum-rated cable jackets which have low flammability but still release toxic and caustic fumes when they are burned.

Low smoke zero halogen is becoming very popular and, in some cases, a requirement where the protection of people and equipment from toxic and corrosive gas is critical. This type of cable is ever involved in a fire very little smoke is produced making this cable an excellent choice for confined places such as ships, submarines, aircraft, high-end server rooms and network centers.

Every coin has two sides. Since LSZH cables have so many benefits listed above, what are the Cons of the cable?

1. LSZH is more susceptible to jacket cracking. Special lubricants have been made to minimize damage during installation.

2. LSZH jacket has a high filler content, around 50% to provide the required flame and smoke performance. This results in a lower mechanical, chemical resistance, water absorption and electrical properties then non LSZH compounds.

3. The current generation of LSZH cables has not yet established a proven history of long time performance.

The LSZH cables are available with 1, 2, 12, 24 fibers, and variable sub-cable dimensions that support specific termination and routing requirements. They are suitable for halogen free and many international installations. LSZH cable contains no flooding gel and is OFNR Riser rated, is perfect for installation in conduits between buildings and run directly thru risers to a convenient network or dome fiber optic splice closure without a separate point of splice at building entrance.

There are also LSZH fiber optic patch cords available. Both LSZH fiber optic cables and LSZH fiber optic patch cords are required for the Rosh compliant cable assemblies, but Rosh standard is more strict besides it require the cables to be LSZH type. LSZH fiber optic patch cords are used widely used in the places where expensive equipment would be damaged if exposed to corrosive gases, and they are also used in crowded areas like commercial centers and sports centers.

ULA Marine Fiber Achieved The Recuction Of 100Gb/s Signal Attenuation

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FiberStore news, OFS, innovative fiber optic network products designer, manufacturer and supplier, recently introduced TeraWave ™ ULA marine optical fiber, which is a new single-mode fiber specially designed for 100 Gb/s coherent transmission of the transmission distance up to 12,000km undersea systems. TeraWave ULA fiber allows more wavelengths with higher transmission speed over sea.

TeraWave ULA is a major breakthrough of marine optical fiber technology, a unique combination of the maximum effective area and excellent cabling performance, but also can greatly reduce the signal attenuation of 100Gb/s reliable coherent transoceanic transmission distance. The effective area of the optical fiber greatly (153 square microns) reduce the nonlinear, allowing to send higher signal power to spans, while improving the signal loss (0.176 dB/km under 1550nm).

For short-distance transmission, such fiber can provide even better nonlinear performance, while improving spectral efficiency.

OFS uses proprietary technology for producing TeraWave ULA fiber, provides low water peak (LWP) performance and low polarization mode dispersion (PMD).

This new fiber is designed for the use of advanced modulation formats and coherent detection distance networks optimization,for example, the greatly distance between the coast and the terminal limit overseas network of DWDM transmission. Compared with previous generations of submarine fiber optic, TeraWave ULA optical fiber can reduce the performance limitations caused by fiber nonlinearity, thus providing higher spectral efficiency and lower repeater spacing.

For applications without using a repeater, hanging cable and deepwater intersection, also can make full use of the large effective area advantage of TeraWave SLA ocean optical fiber, the higher power handling capability without additional distortion, means the longer distance can be distributed more high speed channels before amplification.

For all its marine fiber optic equipment, OFS can be painted and splicing of TeraWave ULA, in order to meet the critical requirements of optical fiber cable. The fiber is carefully selected to meet the specifications of quantity, color, length and transmission properties of customers. And then assembled into a bundle, and the final measurement on the wire harness, to ensure all of its fibers are up to the performance requirements customer specified.

Modern 110 Connecting Blocks For Data Networking

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110 wiring block are one type of punch blocks used to connect sets of wires in a structured cabling system. The “110″ designation is also used to describe a type of insulation-displacement connector used to terminate twisted pair cables which uses a similar punch-down tool as the older 66 block. People are preffered to 110 blocks rather than 66 blocks in high-speed networks because they introduce less crosstalk and allow much higher density terminations, and meet higher bandwidth specifications. Many 110 blocks are certified for use in Category 5 and Category 6 wiring systems, even Category 6a. The 110 block provides an interconnection between patch panels and work area outlets.

Modern homes usually have phone service entering the house to a single 110 block, when it is distributed by on-premises wiring to outlet boxes throughout the home in series or star topology. At the outlet box, cables are punched down to standard RJ-11 sockets, which fit in special faceplates. The 110 block is often used at both ends of Category 5 cable runs through buildings. In switch rooms, 110 blocks are often built into the back of patch panels to terminate cable runs. At the other end, 110 connections may be used with keystone modules that are attached wall plates. In patch panels, the 110 blocks are built directly onto the back where they are terminated. Category 6 – 110 wiring blocks are designed to support Category 6 cabling applications as specified in TIA/EIA-568-B.2-1 with unique spacing that provides superior NEXT performance.

What is the difference between a “110 block” and a “66 block”?

Both 66 and 110 blocks are insulation displacement connection (IDC) devices, which are key to reliable data connections. 66-clip blocks have been the standard for voice connections for many years. 110 blocks are newer and are preferable for computer work, for one thing, they make it easier to preserve the twist in each pair right up to the point of connection.

1. Although 66-clip blocks historically have been used for data, they are not an acceptable connection for Category 5 or higher cabling. The 110-type connection, on the other hand, offers: higher density (more wiring in a smaller space) and better control (less movement of the wires at the connection). Since more and more homes and businesses call for both voice and data connections, it is easy to see why it makes sense to install 110-type devices in most situations. Most cat5e keystone jack also use type 110 terminals for connecting to the wire.

2. The 110 block is a back-to-back connection whereas the 66 block is a side-by-side connection. The 110 block is a smaller unit featuring a two-piece construction of a wire block and a connecting block. Wires are fed into the block from the front, as opposed to the side entry on the 66 block. This helps to reduce the space requirements of the 110 block and reduce overall cost. The 110 block’s construction also provides a quiet front, meaning there is insulation both above and around the contacts. Since the quiet front is lacking on the 66 blocks, a cover is often recommended.

3. 110 blocks have a far superior labeling system that not only snaps into place but is erasable. This is particularly important for post-installation testing and maintenance procedures.

Wiring block enables you to quickly organize and interconnect phone lines and communication cable, preserve the twists in each pair right up to the connection point. Plus, most networking cable equipment also use 110 type terminals for cable connections.

Technology Of Fiber Optic Amplifiers

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In fiber optic communication, the visible-light or infrared (IR) beams carried by a fiber are attenuated as they travel through the material. Then there comes to the fiber optic amplifier which is used to compensate for the wakening of information during the transmission.

Amplifiers are inserted at specific places to boost optical signals in a system where the signals are weak. This boost allows the signals to be successfully transmitted through the remaining cable length. In large networks, a long series of optical fiber amplifiers are placed in a sequence along the entire network link.

Common fiber optical amplifiers include Erbium-Doped Fiber Amplifier (or EDFA Amplifier), Raman fiber amplifier, and silicon optical amplifier (SOA). Erbium doped fiber amplifier is the major type of the fiber amplifier used to boost the signal in the WDM fiber optic system, as we know it is WDM that increase the capacity of the fiber communications system and it is the erbium-doped fiber amplifier that makes WDM transmission possible. Fiber amplifiers are developed to support Dense Wavelength Division Multiplexing (DWDM) which is called DWDM EDFA amplifier and to expand to the other wavelength bands supported by fiber optics.

There are several different physical mechanisms that can be used to amplify a light signal, which correspond to the major types of optical amplifiers. In doped fibre amplifiers and bulk lasers, stimulated emission in the amplifier’s gain medium causes amplification of incoming light. In semiconductor optical amplifiers (SOAs), electron-hole recombination occurs. In Raman amplifiers, Raman scattering of incoming light with phonons in the lattice of the gain medium produces photons coherent with the incoming photons. Parametric amplifiers use parametric amplification.

When light is transmitted through matter, part of the light is scattered in random directions. A small part of the scattered light has frequencies removed from the frequency of the incident beam by quantities equal to the vibration frequencies of the material scattering system. Raman fiber optic amplifiers function within this small scattering range. If the initial beam is sufficiently intense and monochromatic, a threshold can be reached beyond which light at the Raman frequencies is amplified, builds up strongly, and generally exhibits the characteristics of stimulated emission. This is called the stimulated or coherent Raman effect.

EFDA fiber optic amplifier functions by adding erbium, rare earth ions, to the fiber core material as a dopant; typically in levels of a few hundred parts per million. The fiber is highly transparent at the erbium lasing wavelength of two to nine microns. When pumped by a laser diode, optical gain is created, and amplification occurs.

Silicon or semiconductor optical amplifier functions in a similar way to a basic laser. The structure is much the same, with two specially designed slabs of semiconductor material on top of each other, with another material in between them forming the “active layer”. An electrical current is set running through the device in order to excite electrons which can then fall back to the non-excited ground state and give out photons. Incoming optical signal stimulates emission of light at its own wavelength.

Fiber optic repeater also can re-amplify an attenuated signal but it can only function on a specific wavelength and is not suitable for WDM systems. That is the reason why optical fiber amplifier plays a much more important role in communication systems.

The Chanllenges of Technology And Cost 100G Faced

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More and more high bandwidth services such as high definition(HD) video, online games and video conference challenging the traditional network, 100G as a ease network bandwidth technology, becomes the new hope of the operator.

100G industry chain has matured, with all components and subsystems have commercial capacity of multiple manufacturers, the market also needs the support of 100G system, the backbone network will be fully transferred to the 100G-leading era. From the early 2013, the focus point of 100G is from the laboratory into 100G network deployment and the commercial 100G has started.

Four Technical Challenges Of 100G

Although the 100G has been carried out, but the 100G transmission technology meets four technical challenges.

First, high power consumption. The achievement mechanism of 100G technology is complex, the optical receiver requires the use of coherent reception and processing of the DSP, the key chip has no ASIC, resulting in high power consumption of the whole 100G system. When large-scale commercial 100G technology, the average power consumption of each wavelength is still a problem waiting to be solved. Currently the power consumption of per wavelength is above 200W, the average power consumption of per frame is 7000W, so there will need three frames. Obviously, the 28nm process can help to reduce energy consumption, but there is no 100G solution of 28-nanometer. In addition, although the light energy consumption is not large, but due to the use of next-generation optical transceiver will increase greatly, reducing the power consumption is very necessary.

The second is integrated, especially in the field of optical circuit and photoelectric integration. How to add mass active and passive optical devices such as laser, optical amplifier, wavelength division multiplexing(WDM) and transmitter/receiver to the network to achieve highly integrated? Using semiconductor technology to the integration of CWDM and laser?

The third is test. The challenges of 100G testing include the quality evaluation of the deployed 100G system signal and the system maintenance after deployed. 100G using polarization multiplexing, and the signal spectrum is wide, the common OSDR and test instruments can not real-time test it, only by shutting off the laser method. How to achieve real-time test is industry’s future research topic, many of today’s online testing system are worth studying.

The Fourth is few prospective studies. How to make the current transmission system gradually shift to user-oriented management from the traditional network management? Quickly and efficiently allocate the physical resources?

The key is the problem of cost

The key reason why 100G failed to be applied large-scale currently is the opportunity cost is relatively too high. In the era of 100G, the cost of optical module is very high. The mainstream CFP module, the actual sales price is more than $10,000. From the point of optical module cost, 100G module is several times higher than 10G optical module. It also requires manufacturers continue to make efforts in chip integration, integrated optical module miniaturization and system design, to achieve the overall cost of products are reduced.

Especially the regard of optical module technology, the cost of this part is the key of the whole 100G system cost, the optical module itself has to face the challenges of control power consumption and improve board integration.