January 28, 2015

Bacic EDFA-Erbium Doped Fiber Amplifier Design

The transceiver power budget can only deliver up to a certain length of transmission length. Previously, to solve this issue, a repeater or a regenerator would be used. A regenerator also called optical-electrical-optical (OEO) device since it converts the optical signal to an electrical signal, processes this signal (re-amplify, reshape and retime) and then converts back to an optical signal so that the signal can then cover longer distances.

The introduction of optical amplifiers in the 1990s, especially the EDFA (Erbium doped fiber amplifier) conquered the regenerator technology and opened doors to the WDM technology. The EDFAOptical Amplifiers, unlike the repeater, is transparent to the number of channels, bit-rate, protocol, and modulation formats thus revolutionizing the backhaul network (for transoceanic distance) and uplifting the optical communication field and community at large. There are various types of amplifiers depending on the technique of amplifying, namely SOA (semiconductor optical amplifier), EDFA and Raman amplifier.

In its most basic form the EDFA consist of a length of EDF (typically 10-30m), a pump laser, and a component (often referred to as a WDM) for combining the signal and pump wavelength so that they can propagate simultaneously through the EDF. In principle EDFA’s can be designed such that pump energy propagates in the same direction as the signal (forward pumping), the opposite direction to the signal(backward pumping), or both direction together. The pump energy may either by 980nm pump energy, 1480nm pump energy, or a combination of both. Practi cally, the most common EDFA configuration is the forward pumping configuration using 980nm pump energy , as shown in Figure 2. This configuration makes the most efficient use of cost effective, reliable and low power consumption 980nm semiconductor pump laser diodes, thus providing the best overall design with respect to performance and cost trade-offs.

Besides the three basic components described above, Figure 2 also shows additional optical and electronic components used in a basic single stage EDFA. The signal enters the amplifier through the input port, and then passes through a tap which is used to divert a small percentage of the signal power (typically 1-2%) to an input detector. The signal then passes through an isolator, before being combined with pump energy emitted by the 980nm pump laser diode. The combined signal and pump energy propagate along the EDF, where signal amplification occurs, and then the amplifi ed signal exits the EDF and passes through a second isolator. The purpose of the two isolators, which allow light to pass only in a single direction, is to ensure that lasing cannot take place within theCATV amplifier. Furthermore, the output isolator also acts as a filter for 980nm light propagating in the forward direction, thus stopping the 980nm light from exiting the amplifier output port.

In a multi-channel WDM amplifier, a Gain Flattening Filter (GFF) is usually placed following the output isolator in order to flatten the gain spectrum, as shown in Figure 3. The attenuation spectrum of the GFF is designed to match the Gain spectrum of the EDF (operating at a given fixed gain), such that the combination of the two produces a flat gain. Following the GFF the signal passes through an output tap used to divert a small percentage of the output power (typically 1-2%) to the output detec tor. The output and input detectors are used to monitor the input and output power respecti vely, and thus provide feed-back to the control unit, which controls the amplifier by setting the pump laser current, and thus the amount of pump power injected into the EDF. The control unit also provides exter nal communication, for example via an RS232 interface.

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January 21, 2015

Fiber Optic Splitter From Fiberstore

Fiber optic splitter, also named beam splitter, is based on a quartz substrate of integrated waveguide optical power distribution device, the same as coaxial cable transmission system, The optical network system also needs to be an optical signal coupled to the branch distribution, which requires thepassive optical splitter, Is one of the most important passive devices in the optical fiber link, is optical fiber tandem device with many input terminals and many output terminals, Especially applicable to a passive optical network (EPON, GPON, BPON, FTTX, FTTH etc.) to connect the MDF and the terminal equipment and to achieve the branching of the optical signal.

Fiber optic splitter is a key optical device in passive optical network (PON) systems, also known as a passive optical splitter, which splits the optical signal power evenly into all the output ports. In the PON field plant, a1x8 splitterto 1 × 32 splitter is placed on an electric pole, connecting the distribution optical cable in the air and the drop wire to the customer premises. A 1 × N splitter can be part of an N × N star coupler.

A fiber optic splitter is a device that splits the fiber optic light into several parts by a certain ratio. For example, when a beam of fiber optic light transmitted from a 1X4 equal ratio splitter, it will be divided into 4-fiber optic light by equal ratio that is each beam is 1/4 or 25% of the original source one. A fiber optic splitter is different from WDM. WDM can divide the different wavelength fiber optic light into different channels. fiber optic splitter divide the light power and send it to different channels.

Most Splitters available in 900μm loose tube and 250μm bare fiber. 1x2 and 2x2 couplers come standard with a protective metal sleeve to cover the split. Higher output counts are built with a box to protect the splitting components

Features of Fibertronics Splitters Couplers:

Comes in Singlemode, Multimode 62.5, and Multimode 50 Fiber Modes
Built with either 900μm loose tube fiber or 250μm bare fiber
Available unconnectorized or with any fiber optic connector or combination: LC, LC/APC, SC, SC/APC, FC, FC/APC, and ST
1x2 and 2x2 available in many split ratios including: 50/50, 40/60, 30/70, 20/80, 10/90, 5/95, 1/99, 60/40, 70/30, 80/20, 90/10, 95/5, and 99/1

Fiberstore stocks hundreds of fiber optic adapter, fiber coupler, and fiber optic splitter solutions for both Multimode and Single mode fiber applications. We offer ST, SC, FC, LC, MTRJ, and MU style fiber optic adapters and fiber coupler products for just about every fiber cabling design requirement.

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January 19, 2015

Erbium Doped Fiber Amplifier Technology

At the heart of EDFA technology is the Erbium Doped Fiber (EDF), which is a conventional Silica fiber doped with Erbium. When the Erbium is illuminated with light energy at a suitable wavelength (either 980nm or 1480nm) it is excited to a long lifetime intermediate state (see Figure 1), following which it decays back to the ground state by emitting light within the 1525-1565 nm band. If light energy already exist within the 1525-1565nm band, for example due to a signal channel passing through the EDF, then this stimulates the decay process (so called stimulated emission), resulting in additional light energy. Thus, if a pump wavelength and a signal wavelength are simultaneously propagating through an EDF, energy transfer will occur via the Erbium from the pump wavelength to the signal wavelength, resulting in signal amplification.

In its most basic form the EDFA optical amplifier consist of a length of EDF (typically 10-30m), a pump laser, and a component (often referred to as a WDM) for combining the signal and pump wavelength so that they can propagate simultaneously through the EDF. In principle EDFA’s can be designed such that pump energy propagates in the same direction as the signal (forward pumping), the opposite direction to the signal (backward pumping), or both direction together. The pump energy may either by 980nm pump energy, 1480nm pump energy, or a combination of both. Practically, the most common EDFA configuration is the forward pumping configuration using 980nm pump energy, as shown in Figure 2. This configuration makes the most efficient use of cost effective, reliable and low power consumption 980nm semiconductor pump laser diodes, thus providing the best overall design with respect to performance and cost trade-offs.

High Output Power with Class 1M Laser Safety

High capacity reconfigurable networks require high output power in order to maintain acceptable levels of OSNR. On the other hand, a major requirement for optical networks is that they comply with relevant laser safety standards, such as IEC 60825 parts 1 and 2, ITU-T G.664, and CDRH 21 CFR §1040.10. These standards dictate a maximum safe level of laser radiation, known as the Class 1M hazard level, above which exposure to radiation can be potentially harmful to skin and eyes. For EDFA’s operating in the C-Band, the Class 1M hazard level corresponds to a maximum theoretical output power of about 21.3 dBm. In practice however, the specified output power of a Class 1M EDFA should not exceed 20.5dBm, in order to take into account suitable safety margins.

For an EDFA to provide output power above 20.5 dBm, and still retain a Class 1M safety classification, it is necessary to provide an automatic power reduction (APR) mechanism that ensures reduction of output power upon occurrence of any event which could potentially lead to exposure to radiation above the Class 1M hazard level.

The Fiberstore VG EDFA In-line Amplifier Class 1M APR scheme is based on two independent detection mechanisms designed to detected any disruption in the output transmission line up to a distance of a few tens of kilometers, sufficiently far to cover that part of the transmission line where the signal power is above 20.5 dBm. Upon detection of such a disruption, the output power is decreased within 100 ms (in compliance with Class 1M requirements) to a level below 20.5 dBm. The APR hardware supports full redundancy of all critical components, such that there is no single point of failure which could lead to a situation where the EDFA remains operational, while the APR is not in operation.

A complementary feature to the APR mechanism is the automatic restart procedure (ARP). This ensures that when the fiber disruption that caused an APR event is corrected, the EDFA will automatically increase output power to the required level without need for manual operator intervention. These unique and patent protected mechanisms allow Fiberstore EDFAs to be classified as Class 1M laser products, while at the same time providing up to 26 dBm output power.

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January 06, 2015

The More and More Mature Fiber Optic Cables Transmission Technology

Fiber optic media are any network transmission media that generally use glass, or plastic fiber in some special cases, to transmit network data in the form of light pulses. Within the last decade, optical fiber has become an increasingly popular type of network transmission media as the need for higher bandwidth and longer spans continues.

Fiber optic technology is different in its operation than standard copper media because the transmissions are "digital” light pulses instead of electrical voltage transitions. Very simply, fiber optic transmissions encode the ones and zeroes of a digital network transmission by turning on and off the light pulses of a laser light source, of a given wavelength, at very high frequencies. The light source is usually either a laser or some kind of Light-Emitting Diode (LED). The light from the light source is flashed on and off in the pattern of the data being encoded. The light travels inside the fiber until the light signal gets to its intended destination and is read by an optical detector.

Fiber optic cables are optimized for one or more wavelengths of light. The wavelength of a particular light source is the length, measured in nanometers (billionths of a meter, abbreviated "nm”), between wave peaks in a typical light wave from that light source. You can think of a wavelength as the color of the light, and it is equal to the speed of light divided by the frequency. In the case of Single-Mode Fiber (SMF), many different wavelengths of light can be transmitted over the same optical fiber at any one time. This is useful for increasing the transmission capacity of the fiber optic cable since each wavelength of light is a distinct signal. Therefore, many signals can be carried over the same strand of optical fiber. This requires multiple lasers and detectors and is referred to as Wavelength-Division Multiplexing (WDM).

Typically, optical fibers use wavelengths between 850 and 1550 nm, depending on the light source. Specifically, Multi-Mode Fiber (MMF) is used at 850 or 1300 nm and the SMF is typicallyused at 1310, 1490, and 1550 nm (and, in WDM systems, in wavelengths around these primary wavelengths). The latest technology is extending this to 1625 nm for SMF that is being used for next-generation Passive Optical Networks (PON) for FTTH (Fiber-To-The-Home) applications. Silica-based glass is most transparent at these wavelengths, and therefore the transmission is more efficient (there is less attenuation of the signal) in this range. For a reference, visible light (the light that you can see) has wavelengths in the range between 400 and 700 nm. Most fiber optic light sources operate within the near infrared range (between 750 and 2500 nm). You can’t see infrared light, but it is a very effective fiber optic light source.

Above: Multimode fiber is usually 50/125 and 62.5/125 in construction. This means that the core to cladding diameter ratio is 50 microns to 125 microns and 62.5 microns to 125 microns. There are several types of multimode fiber patch cable available today, the most common are multimode SC fiber cable, LC, ST, FC, ect.

Tips: Most traditional fiber optic light sources can only operate within the visible wavelength spectrum and over a range of wavelengths, not at one specific wavelength. Lasers (light amplification by stimulated emission of radiation) and LEDs produce light in a more limited, even single-wavelength, spectrum.

WARNING: Laser light sources used with fiber optic cables (such as the OM3 cables) are extremely hazardous to your vision. Looking directly at the end of a live optical fiber can cause severe damage to your retinas. You could be made permanently blind. Never look at the end of a fiber optic cable without first knowing that no light source is active.

The attenuation of optical fibers (both SMF and MMF) is lower at longer wavelengths. As a result, longer distance communications tends to occur at 1310 and 1550 nm wavelengths over SMF. Typical optical fibers have a larger attenuation at 1385 nm. This water peak is a result of very small amounts (in the part-per-million range) of water incorporated during the manufacturing process. Specifically it is a terminal –OH(hydroxyl) molecule that happens to have its characteristic vibration at the 1385 nm wavelength; thereby contributing to a high attenuation at this wavelength. Historically, communications systems operated on either side of this peak.

When the light pulses reach the destination, a sensor picks up the presence or absence of the light signal and transforms the pulses of light back into electrical signals. The more the light signal scatters or confronts boundaries, the greater the likelihood of signal loss (attenuation). Additionally, every fiber optic connector between signal source and destination presents the possibility for signal loss. Thus, the connectors must be installed correctly at each connection. There are several types of fiber optic connector available today. The most common are: ST, SC, FC, MT-RJ and LC style connectors. All of these types of connectors can be used with either multimode or single mode fiber.

Most LAN/WAN fiber transmission systems use one fiber for transmitting and one for reception. However, the latest technology allows a fiber optic transmitter to transmit in two directions over the same fiber strand (e.g, a passive cwdm mux using WDM technology). The different wavelengths of light do not interfere with each other since the detectors are tuned to only read specific wavelengths. Therefore, the more wavelengths you send over a single strand of optical fiber, the more detectors you need.

Article Source: http://www.cables-solutions.com/the-more-and-more-mature-fiber-optic-cables-transmission-technology.html

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January 05, 2015

Testing Fiber Optic Splitters Or Other Passive Devices

A fiber optic splitter is a device that splits the fiber optic light into several parts by a certain ratio. For example, when a beam of fiber optic light transmitted from a 1X4 equal ratio splitter, it will be divided into 4-fiber optic light by equal ratio that is each beam is 1/4 or 25% of the original source one. A fiber optic splitter is different from WDM. WDM can divide the different wavelength fiber optic light into different channels. fiber optic splitter divide the light power and send it to different channels.

Most Splitters available in 900µm loose tube and 250µm bare fiber. 1×2 and 2×2 couplers come standard with a protective metal sleeve to cover the split. Higher output counts are built with a box to protect the splitting components.

Testing a coupler or splitter (both names are used for the same device) or other passive fiber optic devices like switches is little different from testing a patchcord or cable plant using the two industry standard tests, OFSTP-14 for double-ended loss (connectors on both ends) or FOTP-171 for single-ended testing.

First we should define what these passive devices are. An optical coupler is a passive device that can split or combine signals in optical fibers. They are named by the number of inputs and outputs, so a splitter with one input and 2 outputs is a 1x2 fiber splitter, and a PON splitter with one input and 32 outputs is 1x32 splitter. Some PON splitters have two inputs so it would be a 2X32. Here is a table of typical losses for splitters.

Splitter Ratio

Important Note! Mode Conditioning can be very important to testing couplers. Some of the ways they are manufactured make them very sensitive to mode conditioning, especially multimode but even singlemode couplers. Singlemode couplers should always be tested with a small loop in the launch cable (tied down so it does not change and set the 0dB reference with the loop.) Multimode couplers should be mode conditioned by a mandrel wrap or similar to ensure consistency.

Let’s start with the simplest type. Shown below is a simple 1X2 splitter with one input and two outputs. Basically, in one direction it splits the signal into 2 parts to couple to two fibers. If the split is equal, each fiber will carry a signal that is 3dB less than the input (3dB being a factor of two) plus some excess loss in the coupler and perhaps the connectors on the 1x4 fiber optic splitter module. Going the other direction, signals in either fiber will be combined into the one fiber on the other side. The loss is this direction is a function of how the coupler is made. Some couplers are made by twisting two fibers together and fusing them in high heat, so the coupler is really a 2X2 coupler in which case the loss is the same (3dB plus excess loss) in either direction. Some splitters use optical integrated components, so they can be true splitters and the loss in each direction may different.

coupler

So for this simple 1X2 PLC splitter, how do we test it? Simply follow the same directions for a double-ended loss test. Attach a launch reference cable to the test source of the proper wavelength (some splitters are wavelength dependent), calibrate the output of the launch cable with the meter to set the 0dB reference, attach to the source launch to the splitter, attach a receive launch cable to the output and the meter and measure loss. What you are measuring is the loss of the splitter due to the split ratio, excess loss from the manufacturing process used to make the splitter and the input and output connectors. So the loss you measure is the loss you can expect when you plug the splitter into a cable plant.

To test the loss to the second port, simply move the receive cable to the other port and read the loss from the meter. This same method works with typical PON splitters that are 1 input and 32 outputs. Set the source up on the input and use the meter and reference cable to test each output port in turn.

What about the other direction from all the output ports? (In PON terms, we call that upstream and the other way from the 1 to 32 ports direction downstream.) Simply reverse the direction of the test. If you are tesing a 1X2 splitter, there is just one other port to test, but with a 1X32, you have to move the source 32 times and record the results on the meter.

fiber splitter

What about multiple input and outputs, for example a 2X2 coupler? You would need to test from one input port to the two outputs, then from the other input port to each of the two outputs. This involves a lot of data sometimes but it needs to be tested.

There are other tests that can be performed, including wavelength variations (test at several wavelengths), variations among outputs (compare outputs) and even crosstalk (put a signal on one output and look for signal on other outputs.)

Once installed, the splitter simply becomes one source of loss in the cable plant and is tested as part of that cable plant loss for insertion loss testing. Testing splitters with an OTDR is not the same in each direction.

Other Passive Devices

There are other passive devices that require testing, but the test methods are similar.

Fiber optic switches are devices that can switch an input to one of several outputs under electronic control. Test as you would the splitter as shown above. Switches may be designed for use in only one direction, so check the device specifications to ensure you test in the proper direction. Switches may also need testing for consistency after multiple switch cycles and crosstalk.

Attenuators are used to reduce signal levels at the receiver to prevent overloading the receiver. There is a page on using attenuators that you should read. If you need to test an attenuator alone, not part of a system, use the test for splitters above by using the attenuator to connect the launch and receive cables to see if the loss is as expected.

Wavelength-division multiplexers can be tricky to test because they require sources at a precise wavelenth and spectral width, but otherwise the test procedures are similar to other passive components.

Fiber optic couplers or splitters are available in a wide range of styles and sizes to split or combine light with minimal loss. All couplers are manufactured using a very simple proprietary process that produces reliable, low-cost devices. They are physically rugged and insensitive to operating temperatures. Couplers can be fabricated in custom fiber lengths and/or with terminations of any type.

Fiberstore offers a wide variety of collimation and coupling components that can be used to effectively collimate or couple light out of and into FC/PC, FC/APC, or SMA terminated fiber. OEM manufactuer of Passive fiber optical splitters for PON. 1x2, 1x4, 1x8, 1x16, 1x32, 1x64 optical splitter and 2x N ftth splitter-PLC& singlemode& multimode FBT fiber coupler splitter. Optical isolators help protect sensitive laser sources and components from back reflections while fiber couplers, WDMs, circulators, and switches are the fundamental tools to creating fiber based optical circuits. We also offer a line of components for optogenetics applications, including fiber optic cannulae, patch cords, and light sources.

More about optical fiber information, you can go to fiber opitc components blog, we designs, manufactures, and sells a broad portfolio of optical communication products, including passive optical network, or PON, subsystems, optical transceivers used in the enterprise, access, and metropolitan segments of the market, as well as other optical components, modules, and subsystems.

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January 01, 2015

Excellent Solution to Fiber Patch Cable Management

Recently I saw many people be in trouble in fiber patch cable management, usually see them stack the cables casually, many people will have the feeling of a mess and always envy other people can do it well, maybe today’s article can give you a lot of help and don’t have to be jealous of other people’s good work.

Fiber patch cords have the possibly to be the weakest link in the fiber optic network, usually in order the finish optimum performance and reliability we must observe true procedures in administration of the singlemode simplex fiber, the best solution will be the smallest cost and changes or moves. In the fiber patch cable managements, the voice connection should be also careful. Well, let’s tell you detailed procedures.

patch cable

When we receive the request from the administration, be sure that you know the introduction and design of the fiber cabling and you should also know that if you have fiber patch cords that can match to the stalled cabling, the reason is that fiber optic cables have different types and they should be distinguished. Then choose suitable length of fiber cable. The length depends on its points of connection. It is the shortest one that does not obstruct or interfere with other cords and connectors on the fiber patch panels, avoiding running cords and connectors on the panel. The next step is that tight the patch cable, it will be pulled on connectors and too much slack complicates cable management, making the fiber patch panel more difficult to operate in. At the fiber patch panel, the patch cables equally toward both sides of the vertical cable management channels to prevent overloading one side. Be careful not to mix up cords of different core diameters. Additionally, cords must be of the same or higher bandwidth as the behind-the-wall cabling.

Before the patching, there is a point we need to remember, it is cleaning the connector, the cleaning parts include connector ends on lc to lc fiber patch cord, connector ends on panels, connector ends on network equipment, as for how to clean different types of the fibre optic connector, such as fibre optic sc connector, fibre optic lc connector…We mentioned it in our Fiberstore’s blog, if you are interested in it, welcome to visit Fiberstore’s blog. For example, exceeding the bend radius can result in significant additional loss and adverse impact on channel performance.

For example, mpo fiber cable, the minimum bend radius is ten times the core diameter. Take care not to use excessive force during the patching process. This can stress cords and connectors, reducing their performance. If you need to go to force in pulling a cord, something is wrong. If the existing core is the right length, it may be possible to re-use it. If this is the case, remove the cord completely and re-run it in through the cable pathways. This is the only guaranteed way to ensure there are no tangles, kinks or strains in the cord. The final step is to update the documentation of the as-built configuration and close the work order associated with the completed change request.

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