Optical Amplifier Overview

When it comes to optical fiber communication, we are impressed with its fast speed, large information capacity and bandwidth. To achieve this result, numbers of optical components play key roles in optical systems. Optical amplifier is one of them. When transmitted over long distance, the optical signal will be highly attenuated. On this situation, optical amplifier makes a difference. Today, this article will give a brief overview about optical amplifier to help you learn more about it.

What Is an Optical Amplifier?

Usually a basic optical communication link consists of a transmitter and receiver, with an optical fiber cable connecting them. Even if signals in fibers suffer less attenuation than in other mediums, there is still a limited distance about 100 km. Beyond this distance, the signal will become too noisy to be detected.

Optical amplifier is a device designed to directly amplify an input optical signal, without needing to transform it first to an electronic signal. And at the same time, it can strengthen the signal, which is conducive to transmission over long distances. Here is a comparison figure. In the (a), it is an electrical signal regeneration station. We can see all the channels are separated, signals detected, amplified and cleaned electrically, then transmitted and combined again. However, in the figure (b), it is an optical amplifier in which all channels are optically and transparently amplified together. Compared to electrical amplifier, optical amplifier is more cost-effective. Because it amplifies signals directly, and needs less cost.

comparison

Common Types

Generally, there are three common types optical amplifier: the erbium doped fiber amplifier (EDFA), the semiconductor optical amplifier, and the fiber Raman amplifier.

Erbium Doped Fiber Amplifier (EDFA)

The amplifying medium of EDFA is a glass optical fiber doped with erbium ions. The wavelength near 1550 nm can be amplified effectively in erbium doped optical fiber amplifiers. What’s more, EDFA has low noise and can amplify many wavelengths simultaneously, making EDFA widely used in optical communications. According to the functions, EDFA usually has three types: booster amplifier, in-line amplifier and pre-amplifier.

A booster amplifier operates at the transmission side of the link, designed to amplify the signal channels exiting the transmitter to the level required for launching into the fiber link. It’s not always required in single channel links, but is an essential part in WDM link where the multiplexer attenuates the signal channels. It has high input power, high output power and medium optical gain. The common types are 20dBm Output C-band 40 Channels 26dB Gain Booster EDFA, 16dBm Output C-band 40 Channels 14dB Gain Booster EDFA and so on. Of course, there are still different specification of booster amplifiers which cannot be listed here. Here is a picture of 23dB Output 1550nm Booster EDFA Optical Amplifier.

booster amplifier

An in-line amplifier typically operates in the middle of an optical link, which is designed for optical amplification between two network nodes on the main optical link. It features medium to low input power, high output power, high optical gain, and a low noise figure.

At the end a pre-amplifer makes a difference. Pre-amplifier is used to compensate for losses in a demultiplexer near the optical receiver. It has relatively low input power, medium output power and medium gain.

pre-amplifier.png

Semiconductor Optical Amplifier

Semiconductor optical amplifier (SOA) uses a semiconductor to provide the gain medium. It operates with less power and is cheaper. But its performance is not as good as EDFA. SOA is noisier than EDFA. Therefore, SOA is usually applied in local area networks where performance is not required but the cost is an important factor.

Raman Amplifier

In a fiber Raman amplifier, power is transferred to the optical signal by a nonlinear optical process known as the Raman effect. Distributed and lumped amplifiers are the two common types of Raman amplifier. The transmission fiber in distributed Raman amplifier is utilized as the gain medium by multiplexing a pump wavelength with the signal wavelength, while a lumped Raman amplifier utilizes a dedicated, shorter length of fiber to provide amplification. Here is a Raman amplifier.

raman-amplifier.jpg

Conclusion

Optical amplifiers perform a critical function in modern optical networks, enabling the information transmitted over thousands of kilometers and providing the data capacity which current and future communication networks are required. Amplifiers mentioned above are available in Fiberstore. If you are interested, please visit FS.COM for more information.

Fiber Cleaver – An Essential Tool for Fiber Splicing

In the world of fiber splicing, fiber cleaver is an important tool that cleaves the fibers to be spliced precisely. It is the warranty of a good splicing because the quality of the splice will depend on the quality of the cleave. And high quality fiber breaks with clean surfaces are the yardstick for good fiber cleavers. This article will provide some knowledge about fiber cleavers.

Basics of Fiber Cleaver

In optical fiber, a cleave means a controlled break that intentionally creates a perfect flat end face which is perpendicular to the longitudinal axis of the fiber. Fiber optic cleaver is used in most production lines. It can give a precise cut at a cleave angle of 90 degrees to the fiber end. Cleavers are available for both single fiber or ribbon fibers.

Two kinds of fiber cleavers are often seen in the market. First is the pen-shaped scribe cleaver, which looks like a ballpoint pen. It has small wedge tip made of diamond or other hard materials. Scribe cleaver is a traditionally low-cost fiber cleaving tool using the scribe-and-pull method to cleave the fiber. The operator may scribe the fiber manually and then pull the fiber to break it. But it is difficult to achieve high cleaving accuracy by this tool.

scribe-cleaver

Therefore, in order to solve the problem of accuracy, the precision cleaver is introduced to the industry. This might cost you much higher than the scribe cleaver, but your working speed and efficiency can be greatly improved since multiple fibers can be cleaved at one time. With the extensive applications of fusion splicers, precision cleavers are favored by operators to avoid splice loss.

precision-cleaver

How to Use Precision Cleaver?

Precision cleaver is the mechanical device, which looks a little difficult for novices to deal with. Here are some simple steps that you can follow when using the precision cleaver:

  • Step one, open the fiber clamp.
  • Step two, press down on the button and slide the carriage back.
  • Step three, move the fiber slide back until it stops.
  • Step four, clean the stripped fiber with a solution of greater than 91% ISO alcohol.
  • Step five, place the stripped and cleaned fiber into the slot at the desired cleave length.
  • Step six, while maintaining firm pressure on the buffer, move the fiber slide forward until it stops.
  • Step seven, close the fiber clamp.
  • Step eight, slide the carriage forward.
  • Step nine, lift the fiber clamp.
  • Step ten, move the fiber slide back.
  • Step eleven, remove the fiber, which is now cleaved to the proper length.
  • Step twelve, remove and properly dispose of the scrap fiber.
Precautions for Fiber Cleaving

Make sure you comply with these precautions during the process of fiber cleaving:

  • First, wear a pair of safety glasses. This can protect your eyes from accidental injury. It is highly recommended when handling chemicals and cleaving fiber.
  • Second, be careful when using ISO alcohol. Keep the ISO alcohol away from heat, sparks and open flame. This is because the ISO alcohol is flammable under the flash point of 73° F. It can also cause irritation to eyes on contact. In case of eye contact, flush eyes with water for at least 15 minutes. Moreover, inhaling fumes may induce mild narcosis. In case of ingestion, consult a physician.
  • Third, store cleaved glass fibers in proper place. Since cleaved glass fibers are very sharp and can pierce the skin easily. Do not let cut pieces of fiber stick to your clothing or drop in the work area where they can cause injury later. Use tweezers to pick up cut or broken pieces of the glass fibers and place them on a loop of tape kept for that purpose alone.
Conclusion

Having a qualified fiber cleaver enhances the cleaving precision and efficiency. Nowadays, precision cleaver has been widely applied to accurate fusion splicing. Proper investment is valuable for the long-term applications. If you want to get one for your project, FS.COM is a good place to go.

Finding a Perfect Fiber Media Converter for Your Network

Fiber media converter or fiber converter is a device that links two different media signals for conversion, usually exchanging the signals on a copper cable with signals on an optic fiber cable. This device is often used in MAN (metropolitan area network) access and data transport services to enterprise customers. Fiber media converter provides a balanced flow, isolation, conflict and detection of errors and other functions to ensure high security and stability of data transmission. It also breaks the restriction of the Ethernet cable length to more than one hundred meters.

For a long time, fiber media converter is an indispensable part of the actual network set up. And it will continue to transform towards the orientation of high intelligence, high stability, easy management and low cost. Of course, selecting a right fiber media converter is also very essential to the actual applications. This article will mainly introduce some aspects to be considered when purchasing the fiber media converter.

fiber-media-converter

Knowing Function of Fiber Media Converter

Knowing the function of fiber media converter helps you have a better understanding of your own system which contributes to the selection process. Generally speaking, fiber media converter receives data signals from one media and converts them to another while remaining invisible to data traffic and other net devices. It supports quality of service and layer 3 switching since it has no interference with upper-level protocol information. Fiber media converter changes the format of an Ethernet-based signal on twisted pairs into a format compatible with fiber optics. At the other end of the fiber cable run, a second media converter is used to change the data back to its original format.

Fiber media converter supports full duplex Ethernet over UTP at 20 or 200 Mbps, and half-duplex Ethernet over UTP at 10 or 100 Mbps. Full duplex Ethernet is more efficient for connecting two switches or one switch to a file server. Also, fiber optic media converter can automatically sense which mode is in operation without any adjustment for mode switching.

Other Factors to Consider During Your Selection

Here are some factors that you can consider when purchasing a fiber media converter:

  • First, according to different data rates, there are various fiber media converters to match the transmission speeds. Thus, data rates should be considered as an important factor.
  • Second, figure out what transmission media are in your network, and find the corresponding cable types. For instance, there are fiber to copper, single-mode fiber to multimode fiber, dual strand to single strand and so on.
  • Third, diverse fiber media converters have different port types. Typically, there are two types of ports, one for copper and the other for fiber. The copper ports are all designed for RJ45 copper cables. But in terms of fiber ports, there are also another two types. One is designed for fiber optic transceivers (SFP, XFP, etc), and the other for fiber optic patch cables (SC, LC, etc).
  • Fourth, transmission distances of fiber media converters are varied to satisfy different length demands.
  • Fifth, if main power is not available or difficult to deliver in physical locations, PoE fiber media converter can be an option to supply the required power.
  • Sixth, different power supplies are also available. For example, AC (alternating current) power supply, DC (direct current) power supply, internal power supply and external power supply are the common choices.
Applications

Fiber optic converters can be used in lots of applications. Here are some examples. Point to point application can connect two UTP Ethernet switches (or routers, servers, hubs, etc.) via fiber, or to connect UTP devices to workstations and file servers.

point-to-point-media-converter-application

10G Ethernet application extends distances between 10G switches and servers.

10G-Ethernet-media-converter-application

Multimode to single-mode application extends a multimode network across single-mode fiber with distances up to 160 km.

multimode-to-singlemode-media-converter-application

Conclusion

Fiber media converter plays an important role in today’s multi-protocol, mixed media networks. Many types of fiber media converters like fiber to RJ45 converters, SFP Ethernet converters are purchasable on the market now. Please regard this article as an reference for finding a suitable fiber media converter in your network.

Guide to CWDM MUX/DEMUX System Installation

CWDM (coarse wavelength division multiplexing) comes from the WDM system. It is designed to increase the capacity of a fiber optic network without adding additional fiber. The wavelengths of CWDM channels are spaced 20 nm apart which allows the use of low-cost, uncooled lasers. The wavelengths usually range from 1270 nm to 1610 nm.

Today, CWDM Mux/Demux (multiplexer/demultiplexer) module is an important device to increase the current fiber cable capacity by transmitting multiple wavelengths with up to 18 signal channels over a single fiber. When using a CWDM multiplexer at the beginning of the network, accordingly a CWDM demultiplexer should be used at the opposite end to separate the wavelengths and direct them into the correct receivers. This greatly reduces the number of fiber cables and other data links.

CWDM-Mux-and-Demux

Basic Components of CWDM MUX/DEMUX System

Several basic components constitute a CWDM Mux/Demux system. They are a local unit, a remote unit, a rack-mount chassis, CWDM Mux/Demux modules, CWDM SFP transceivers and single-mode patch cables. The local unit and remote unit are two different switches. The rack-mount chassis is needed to be installed for holding the CWDM Mux/Demux module. As for the connections, CWDM SFP transceivers are usually used between a CWDM Mux/Demux module and a switch, and single-mode patch cables are used to connect transceivers to the module.

Preparation Before Installation

Multiple single-mode patch cables are needed for CWDM Mux/Demux system connection. And the transceivers used in the system must support the wavelengths from 1270 nm to 1610 nm. Make sure the installation environment is in a dry and interior space. The module should have enough room to create airflow for easier heat distribution. Any inappropriate arrangement that obstructs the ventilation holes should also be avoided.

CWDM MUX/DEMUX System Installation

Step one, mount the system chassis on the rack. The CWDM rack-mount chassis can be mounted in a standard 19-inch cabinet or rack. Make sure that you install the rack-mount chassis in the same rack or an adjacent rack to your system so that you can connect all the cables between your CWDM Mux/Demux modules and the CWDM SFP transceivers.

mounting-system-chassis

Step two, install the CWDM Mux/Demux modules. You should first loose the captive screws on the blank of module panel and remove the panel. Then align the module with the slot of the chassis shelf and gently push the module into the slot. Finally, ensure that you line up the captive screws on the module with the screw holes on the shelf and tighten them up.

installing-CWDM-MuxDemux-modules

Step three, install CWDM SFP transceivers. Since each channel has a specific wavelength, transceivers must comply with the right wavelengths. Each wavelength must not appear more than once in the system. Device pairs must carry transceivers with the same wavelength.

CWDM-SFP-transceiver

Step four, install the CWDM Mux/Demux to the switch. After inserting the CWDM SFP transceiver into the switch, single-mode patch cables are used to connect the transceiver to the CWDM Mux/Demux module.

Step five, connect the CWDM MUX/DEMUX pairs. In a CWDM MUX/DEMUX system, multiplexer and demultiplexer must be installed in pairs. Two strands of single-mode patch cables are needed in the duplex Mux/Demux module, and one strand of single-mode patch cable is enough for the simplex Mux/Demux module.

When you finish all these steps, the installation of CWDM Mux/Demux system is successfully completed.

Conclusion

CWDM Mux/Demux system is definitely a good solution to high capacity data transmission. It is efficient for power, space and cost saving. And the installation procedure is easy to follow. All the components above are available in FS.COM. If you are interested, please come and visit our website for more information.

Fiber Termination Box – Solution for FTTH Network

In the FTTH network, cable management is a real task. In order to transmit signals to multiple terminations, large amount of optical pigtails are used in the cabling system. A solution must be found to solve the problem of cable routing. Luckily, the advent of fiber termination box has efficiently handled the crux by accommodating and protecting the fiber cables.

Specifically, fiber termination box (FTB), namely optical termination box (OTB), is a kind of fiber optic management product used to distribute and protect the optical fiber links in FTTH Network. Owing to its compact and small size, it is also considered to be the mini version of fiber optic patch panel or optical distribution frame (ODF). The number of ports in fiber termination box is varied from 8 ports to 96 ports, you may choose the right box according to your cable needs.

Fiber Termination Box Types
  • Wall Mount vs. Rack Mount

In terms of different designs, fiber termination box can be classified into wall mount and rack mount types. Wall mount fiber termination box is a perfect solution to be used in building entrance terminals, telecommunication closets, main cross-connects, computer rooms and other controlled environments. It is a suitable device for pre-connectorized cables, field installation of connectors and field splicing of pigtails.

wall-mount-FTB

Rack mount fiber termination box is designed for cross-connect and interconnect architecture which has interfaces between outside plant cables and transmission equipment. And the box unit provides space for fiber splicing, distribution, termination, patching, storage and management.

rack-mount-FTB

  • Indoor vs. Outdoor

With regard to wall mount fiber termination box, it has another two classifications of indoor and outdoor types. Obviously, this is categorized according to the installation site. As the transition point between the riser and the horizontal cable, indoor wall mount fiber termination box offers the operator with optimal flexibility. It serves as the storage place for extended and terminated fibers or as the splice point for spliced fibers.

indoor-wall-mount-FTB

Outdoor wall mount fiber termination box is also used for fiber splicing, termination, and cable management. But its enclosure is usually sealed to prevent cables from environmental damages in FTTH network.

outdoor-wall-mount-FTB

Applications

Fiber termination box is typically applied to telecom equipment room or network equipment room. It is also available for the distribution and termination connection for various kinds of fiber optic systems, and is especially suitable for mini-network terminal distribution in which the optical cables, patch cores or pigtails are connected.

Distinctions Between Fiber Termination Box and Fiber Splice Tray

Sometimes, people may mix the fiber termination box with fiber splice tray due to the similar inside structure. Besides other applications, fiber termination box is often used as the terminal junction where a single cable is spliced into multiple optical pigtails that have connectors at one end and no connector at the other end. Sometimes, fiber splice tray is inside the fiber termination box to contain the spliced fibers. But it can also be employed for independent use to protect the spliced fibers. Thus, these two devices are not interchangeable.

Conclusion

In conclusion, fiber termination box is an important device used for protecting and distributing optical fiber links. The utilization of fiber termination box greatly eases the stress of cable management in FTTH network. Wall mount both indoor and outdoor FTBs and rack mount FTBs are widely deployed for optical communication infrastructures. Of course, a right selection will also contribute to your network.

Effective CWDM & DWDM Mux/Demux Solutions for WDM System

Wavelength division multiplexing (WDM) system is designed for high capacity communications. It is now frequently used as a method to merge multiple optical signals with different wavelengths onto a single fiber. There are two divisions of WDM system: coarse wavelength division multiplexing (CWDM) and dense wavelength division multiplexing (DWDM). Using WDM can enhance the effectiveness of bandwidth in fiber optic communications. The WDM Mux/Demux has a number of communication channels, and matches with a certain frequency. Wavelengths are separated to different receivers at the destination. Mux/Demux module is an important assembly using WDM technology. This article will introduce some effective CWDM and DWDM Mux/Demux solutions for WDM system.

CWDM Mux/Demux & DWDM Mux/Demux
CWDM Mux/Demux

CWDM Mux/Demux is a flexible network solution for WDM optical networks. At most 18 full-duplex wavelengths can be added over a single fiber trunk which greatly alleviates fiber exhaustion. With low insertion loss and high stability, CWDM Mux/Demux is applied to many operations, such as CATV links, WDM systems, test and measurement, metro and access networks, FTTH networks, etc. The deployment of CWDM Mux/Demux is transparent and clear. Its compact form factor enables a much easier manipulation. Only coarse wavelengths can be transmitted over the fiber which reduces the WDM system cost.

Three kinds of CWDM Mux/Demux are widely used in the application. They are 1RU 19″ rack chassis CWDM Mux/Demux, half 19″/1RU CWDM Mux/Demux and splice/pigtailed CWDM Mux/Demux. CWDM Mux/Demux in 19 inch rack mount package is often used for CWDM, EPON and CATV network. Half 19″/1RU CWDM Mux/Demux is packed in LGX box using thing film coating and non-flux metal bonding micro optics packaging. Splice/pigtailed CWDM Mux/Demux is packed in the ABS box package based on standard thin film filter (TFF) technology.

DWDM Mux/Demux

DWDM Mux/Demux conveys optical signals in a more dense wavelength. It is especially used for long distance transmission where wavelengths are highly-packed together. The maximum delivered wavelengths can reach up to 48 channels in 100GHz grid (0.8nm) and 96 channels in 50GHz grid (0.4nm). DWDM Mux/Demux uses a reliable passive WDM technology that achieves low insertion loss. And it provides a solution for adding WDM technology to any existing network device. Applications like point-to-point DWDM fiber optimization, linear add/drop DWDM fiber optimization, external optical monitoring are typically using DWDM Mux/Demux module.

Likewise, 1RU 19″ rack chassis DWDM Mux/Demux, Half 19″/1RU DWDM Mux/Demux and splice/pigtailed DWDM Mux/Demux are three divisions of DWDM Mux/Demux modules. The first type is in 19 inch rack mount package used for long-haul transmission over C-band range of wavelengths. The second one is in LGX package used for PDH, SDH/SONET, Ethernet services transmission. The last one is in ABS box package and its pigtails are labeled with wavelengths.

Effective CWDM Mux/Demux & DWDM Mux/Demux Solutions

18-CH CWDM Mux/Demux is a highly recommended 1RU rack-mount CWDM Mux/Demux that combines 18 CWDM sources on a single fiber. The insertion loss is below 4.9 dB. Moreover, it has a monitor port that enables maintenance without ceasing the operation.

18ch-cwdm-mux-demux

40-CH DWDM Mux/Demux has 40 channels. As a DWDM Mux/Demux module with high density, low-loss and independent 1RU rack mount package, the best utilization of this device is to employ it for high density applications over long-haul transmission. It multiplexes and demultiplexes 40 DWDM wavelengths with 100 GHz in a ring or point-point network. It is a highly cost-effective DWDM Mux/Demux module.

40ch-dwdm-mux-demux

Conclusion

To improve the efficiency of network transmission, WDM technology is often deployed in the devices. 18-CH CWDM Mux/Demux and 40-CH DWDM Mux/Demux are now recommended as the most cost-effective WDM solutions with expanded fiber capabilities. Hope you can choose and use them wisely.

What is Fiber Optic Isolator?

Fiber optic isolator is a passive component used for fiber optic communications. As a magneto-optic device, the purpose of optical isolator is to allow light to be transmitted in only one direction. This helps prevent laser source from unwanted feedback which will damage the laser source or arouse unexpected laser problems, such as mode hop, amplitude modulate, frequency shift and so on. Therefore, isolator is an useful and indispensable device to reduce these effects. In the following parts, fiber optic isolator’s construction, operating principle and classifications will be discussed.

optical-isolator

Construction of Optical Isolator

Fiber optic isolator includes three main parts of an input polarizer, a Faraday rotator with magnet, and an output polarizer. Only linearly polarized light can pass through the input polarizer into the Faraday rotator. The function of the Faraday rotator is to rotate the input light by a certain angle before it reaches the output polarizer. This allows the light in the forward direction to pass unimpeded. However, the light in the reverse direction will not be able to pass the optical isolator and is either reflected or absorbed. These three components of optical isolator skillfully work together and ensure the normal transmission of light signals.

Operation of Optical Isolator

The operation of optical isolator is based on the Faraday effect which was discovered by Michael Faraday in 1842. Faraday effect refers to a phenomenon that the plane of polarized light rotates while transmitting through glass (or other materials) that is exposed to a magnetic field. The rotation direction depends on the direction of the magnetic field instead of the direction of light transmission.

According to different light directions, there are two types of operation modes. One is the forward mode and the other is the backward mode. The forward mode enables light enter into the input polarizer and become linearly polarized. When laser light reaches the Faraday rotator, the Faraday rotator rod will rotate by 45° polarization. Thus, the light finally leaves the output polarizer at 45° polarization. However in the backward mode, the light first enters into the output polarizer with a 45° polarization. Next, as it passes through the Faraday rotator, it continues to be rotated for anther 45° in the same direction. Then the light of 90° polarization becomes vertical to the input polarizer and can not leave the isolator. As a result, the light will be either reflected or absorbed.

optical-isolator-operation

Types of Optical Isolator
1) Polarized Optical Isolator

Polarized optical isolator employs the polarization axis to keep light transmit in one direction. It allows light to propagate forward freely, but disallows any light to travel back. Also, there are dependent and independent polarized optical isolators. The latter is more complicated and often used in EDFA optical amplifier.

2) Composite Optical Isolator

Composite optical isolator is actually a type of independent polarized optical isolator. It is used in EDFA optical amplifier which consists of many other components, such as erbium-doped fiber, wavelength-division multiplexer, pumping diode laser and so on. Since there are many other components in EDFA module, this type of isolator is named as composite optical isolator.

3) Magnetic Optical Isolator

Magnetic optical isolator is essentially the polarized optical isolator in another expression. It stresses the magnetic part of a Faraday rotator. The Faraday rotator is generally a rod made of a magnetic crystal under strong magnetic field with Faraday effect.

Conclusion

In summary, fiber optic isolator guarantees the stable function of laser transmitter and amplifiers by eliminating unnecessary lights. It also ensures a higher performance of light transmission. Using fiber optic isolator is no doubt a good choice for your network.

What is Fiber Optic Attenuator?

In optical data communication, receiving either too much or too little optical power will cause high bit error rates. The receiver amplifier will saturate if power is excessive, or generate noise when interferes with the signal if power is insufficient. In order to solve the problem of too much optical power at the receiver, using a fiber optic attenuator is a good solution.

Fiber optic attenuator or optical attenuator is a passive device used to reduce the power level of an optical signal without appreciably distorting the waveform. To achieve power loss, technologies including air-gap, absorption, scattering, and interference filter are often used for the attenuator products. Fiber optic attenuator can be fixed, manually or electrically adjustable. Furthermore, according to different types of connectors, there are also various classifications of optical attenuators as LC, SC, ST, FC, MU or E2000, etc. This article will introduce some basic working principles and commonly used types of optical attenuators.

Working Principles

With the development of optical technologies, fiber optical attenuator has adopted many principles to help reduce optical power. Here are some of the working principles applied to the fiber optical attenuator:

    • Gap-loss Principle: Gap-loss principle uses an in-line configuration when inserting the optical attenuator in the fiber path to reduce the optical power level. The gap enables light to spread out as soon as it leaves the fiber end from the transmitter. Then some of the light will enter the fiber cladding before it reaches the receiver. However, optical attenuator using gap-loss principle is sensitive to the modal distribution, which means it should be placed near the optical transmitter. Otherwise, the attenuator will be less effective to get enough power loss if being put far away from the transmitter. This kind of problem can be avoided when using the absorptive or reflective principles.
Gap-loss-Principle

Gap-loss Principle

    • Absorptive Principle: Absorptive principle or absorption reduces the light power by using the material in the optical path to absorb optical energy. This can be realized because optical fiber has the defect of absorbing optical energy and converting it into heat. It is both easy and effective to employ absorptive principle to obtain power loss.
Absorptive-Principle

Absorptive Principle

  • Reflective Principle: Reflective principle or scattering causes the signal to scatter which is also a deficiency of optic fiber. The scattered light interferes with fiber to reduce the signal power. Since the material in attenuator is used to reflect a known quantity of the signal, only a desired portion of signal can be transmitted.
Reflective-Principle

Reflective Principle

Common Fiber Optic Attenuator Types
    • Fixed Attenuator: Fixed attenuator is able to deliver a precise power output when the desired level of attenuation is determined. It is usually applied to balance power between fibers and multifiber systems and reduce receiver saturation. Fixed attenuator is typically available in plug and inline styles for single-mode applications. Inline type looks like the ordinary fiber patch cord with the termination of two connectors. Plug type has a bulk head fiber connector with a male end and a female end.

fixed-fiber-optic-attenuator

  • Variable Attenuator: Variable attenuator delivers a precise power output at multiple decibel loss levels with flexible adjustment. The attenuation is easily modified to any level by simple adjustment controls. Variable attenuators can be further categorized as stepwise variable attenuator and continuously variable attenuator. The former changes the attenuation of signal in known steps such as 0.1 dB, 0.5 dB or 1 dB for multiple power sources applications. The latter allows attenuation to be changed on demand without any interruption to the circuit in uncontrolled environments where the input or output needs continuous change.

variable-fiber-optic-attenuator

Conclusion

Fiber optic attenuator is an essential component for reducing optical power in data transmission. Signals achieve a more precise power level with the help of optical attenuators. According to different applications, you’d better choose the most appropriate type of optical attenuators for your system. Hope this article can provide some help for your future selection of optical attenuators.

Cable Shielding of Twisted Pair

For the purpose of providing a reliable connection between electronic devices, choosing a proper shielded twisted pair cable is essential to the network using copper cables. EMI (electromagnetic interference) is a disturbance in twisted pair cables. It affects the performance of an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. But with the help of cable shielding, cables can be immune to the disturbance and keep a stable connection. And this article will present some knowledge about cable shielding. Hope you can find it useful.

STP vs. UTP

Before getting to know cable shielding, you may wonder about the real difference between shielded twisted pair (STP) and unshielded twisted pair (UTP). As their names suggest, STP has a shield that works as a guard and drains the induced current surges to earth. Yet UTP has no cable shield with such a function. But the shortcoming of STP cables is the extra shielding cost added to an installation. Typically, STP cables are more expensive than UTP cables. And due to the stiffer and heavier shielding, coping with STP cables is more difficult. But if you pursue a higher performance, STP will be a preferable choice.

Types of Shields

There are mainly two types of shields: braided shield and foiled shield. Braided shield is made up of woven mesh of bare or tinned copper wires. It has better conductivity than aluminum and more bulk for conducting noise. An easier attachment with connectors can be achieved by crimping and soldering the braid. However, braided shield does not possess 100% coverage. It usually provides 70% to 95% coverage according to the tightness of weave. But as a matter of fact, 70% coverage is always sufficient if cables are fixed. Another shielding is foiled shield. This type of shielding uses a thin layer of aluminum and has a 100% coverage around the conductors. But the drawback is that its conductivity is lower than copper braided shield.

braided-shield-and-foiled-shield

Different Constructions of Shielding

Today, people will use acronyms to name different shielding constructions. Take U/FTP as an example, the first letter “U” represents the outer shield or overall shield of cable, and the followed letter “F” represents the individual shield under the overall shield of each twisted pair or quad.

shielding-construction

Here are some commonly used shielding constructions:

1) Individual Shield

U/FTP is the typical individual shielding using aluminum foil. This kind of construction has one shield for each twisted pair or quad above the conductor and insulation. Individual shield especially protects neighboring pairs from crosstalk.

2) Overall Shield

F/UTP, S/UTP, and SF/UTP are overall shielding with different shield materials. Overall shield refers to the entire coverage around the whole cable. This type of shielding helps prevent EMI from entering or exiting the cable.

3) Individual and Overall Shield

F/FTP, S/FTP, and SF/FTP are individual and overall shield. This type of construction has both layers of shielding. And its immunity to EMI disturbance is greatly improved.

Meanings of the abbreviated letters:
U = unshielded
F = foiled shielding
S = braided shielding
TP = twisted pair

Applications

As for the application in 10GBASE-T Ethernet, UTP, U/FTP, F/UTP, F/FTP and S/FTP are often used. But their practicable cable categories are varied from cat 6/6a to cat 7/7a. When twisted pair cable is deployed for 40GBASE-T Ethernet, U/FTP, F/UTP, F/FTP, S/FTP are applied under cat 8/8.1/8.2.

Conclusion

Adopting twisted pair cable shielding is an effective method to prevent EMI from interfering signal transmission. And there are different shielding constructions for you to choose. Of course, using twisted pair without cable shielding is also feasible if your budget is limited. Wish you find the most suitable twisted pair cable for your project!

Take Cable Management Seriously

In a data center, it is common to see messy cables all over the place. Finding out the right cable becomes a nightmare. However, there are also good examples for well-organized cables that eliminate all the redundant operations due to cable mess. This is the magic of cable management. Typically, cable management is a solution used for the installation of equipment in order to secure cables for electrical services. An orderly data center will greatly enhance the working efficiency and ordinary people are more willing to work in a tidy environment. Therefore, cable management is very necessary for data center cabling.

cable-managemet

Bad Cable Management and Good Cable Management

Benefits of Cable Management

With the help of cable management, there are many advantages that facilitate the work in data center:

1) Ease of Cable Connection

A good cable management can not only provide access to cables but also to devices they are connected to. If cables are tangled together, it will increase the difficulty for handling devices. And working hours are extended for a simple task. But if your cables are well-managed, the connection between cables and devices will be clear to see so as to finish work in a shorter time.

2) Avoid the Risk of Fire

If cables are not under maintenance for a long time, sparks will be easily caused in tangled cables. And the worst result will be a fire. In addition, when a person passes by the cable mess, he is more likely to be stumbled by the cables. Thus the risk of fire is also immensely increased. To avoid such situation, cable management takes an important role for fire safety.

3) Convenient Troubleshooting

While doing the routine troubleshooting in data center, cable testing is one of the steps. However, a huge amount of messy cables makes such a simple task into a complicated one and you have no idea how long it will take to finish the job. But thanks to cable management, you can easily maintain and change cables in order. The process is more convenient if cables are organized well.

Suggestions for Good Cable Management

To achieve a good cable management, here are some useful suggestions:

1) Let in Airflow

Enough airflow will reduce the temperature of surroundings and components for lowering the risk of fire. But the tangled cables will block the air from flowing. Therefore, sorting out the cables to leave enough space for air flowing is very essential. Also, fans can be used as a way to create sufficient airflow to cool down the temperature more promptly.

2) Clean the Dust

A good cable management is always along with dust cleaning. If too much dust enters through the components, the efficiency of devices will be influenced. But the best part for a good cable management is that the open surfaces exposed to dust are greatly reduced, so the cleaning process is a lot easier.

3) Neat Appearance

First impression is always important for the judgment of a good cable management, thus keeping a nice appearance is necessary. The basic rule of managing cables is to make them in a neat order. Then a little imagination can be added to make the appearance more creative.

4) Use Proper Tools

Proper tools are needed for cable management because they can improve the efficiency of your work. Tools like cable wrap, screwdriver, wire scissors, pliers, cable ties, rubber band, etc. are recommended. These instruments makes the process more convenient and easier.

Conclusion

You may think of cable management as a tedious and time-consuming task. But as for the long-term benefit, cable management can prevent device from damage and save time for routine maintenance. Thus better take it seriously for the best of your work in data center.