BiDi Transceiver Overview

For several years ago, when talked about fiber optic transceiver, almost most of people engaged in telecommunication industry would tell that a transceiver is a device comprising both a transmitter and a receiver which are combined and share common circuitry. Almost all fiber optic transceivers uses two fibers to transmit data between routers and switches. One fiber is devoted to transmitting data to the networking equipment, while the other one is devoted to receiving data from the networking equipment. For recent years, a new kind of fiber optic transceiver has been available — Bi-Directional transceiver (BiDi transceiver).

BiDi Transceiver Basis

BiDi transceiver is a type of fiber optic transceiver which uses WDM (wavelength division multiplexing) bi-directional transmission technology so that it can achieve the transmission of optical channels on a fiber propagating simultaneously in both directions. BiDi transceiver is only with one port which uses an integral bidirectional coupler to transmit and receive signals over a single optical fiber (see the following picture). BiDi transceivers are specifically designed for the high-performance integrated duplex data link over a single optical fiber and used in bi-directional communication applications. The BiDi transceivers interface a network device mother board (for a switch, router or similar device) to a fiber optic or unshielded twisted pair networking cable.

Working Principle of BiDi Transceiver

The difference between BiDi transceivers and the two-fiber optical transceiver mainly lies in that BiDi transceivers are fitted with WDM couplers, also known as diplexers, which help to combine and separate data transmitted over a single fiber based on the wavelengths of the light. So BiDi transceivers are also called WDM transceivers. BiDi transceivers are usually deployed in matched pairs to get the work most efficiently. And the diplexers of BiDi transceivers are tuned to match the expected wavelength of the transmitter and receiver that they will be transmitting data from or to.

As can be seen from the following diagram, the paired BiDi transceivers are being used to connect two devices. Device A is used to get upstream data, and Device B is used to get downstream data. Tx means transmit. Rx means receive. The diplexer in one transceiver (Device A) should have a transmitting wavelength of 1310 nm and have a receiving wavelength of 1550 nm. The diplexer in the other transceiver (Device B) should have a transmitting wavelength of 1550 nm and have a receiving wavelength of 1310 nm.

Advantages of BiDi Transceiver

The decisive advantage of using BiDi transceiver is that it helps to reduce the cost of fiber cabling infrastructure. This is caused by reducing the number of fiber path panel ports as well as reducing the amount of tray space dedicated to fiber management. The deployment of BiDi transceiver enables the bandwidth capacity of the optical fiber to be doubled.

 

Fiberstore BiDi Transceiver Solution

Fiberstore supplies a series of BiDi transceivers with different types such as BiDi SFP. These BiDi SFP transceivers support Fast Ethernet, Gigabit Ethernet, and Fibre Channel, etc. And they can be available for simplex SC or LC connector interface, which is used for data transmitting and receiving. Also, the BiDi SFPs from Fiberstore are able to support a wide range of physical media from copper to long-wave single-mode optical fiber with transmission distance up to hundreds of kilometers. The most typical Tx and Rx wavelength combinations are 1310/1490 nm, 1310/1550 nm and 1490/1550 nm. Fiberstore has a large selection of BiDi transceivers in stock. Choosing a Fiberstore BiDi transceiver can help your fiber optic network to be most economical and efficient.

Originally published: www.fiber-optic-components.com/

SC Connector Overview

SC connector was developed by the laboratories at Nippon Telegraph and Telephone (NTT) in 1980s, hitting the market strongly after the advent of ceramic ferrules as the first connector. SC stands for “square connector” or “subscriber connector”, which is a push-on, pull-off connector with a locking tab. It has a push-pull coupling end face with a spring loaded ceramic ferrule by which SC connector can provide for accurate alignment. Commonly, it can be used with singlemode and multimode fiber optic cables with low cost, simplicity, and durability. Due to its excellent performance, it dominated fiber optics for over a decade and still plays an important part now.

SC Connector Structure

The picture below has given a visualized description of the most common elements in SC connector. It is mainly made up of the fiber ferrule, connector sub-assembly body, connector housing, fiber cable and stress relief boot.

The fiber ferrule - In the heart of SC connector, there is a long cylindrical 2.5mm diameter ferrule which is made of ceramic or metal. The ferrule has a hole about 124~127um diameter in its center, so that the stripped bare fiber can be inserted through it. The end of the fiber is at the end of the ferrule, where it typically is polished smooth.

The connector sub-assembly body - The ferrule is then assembled in the SC sub-assembly body. The end of the ferrule protrudes out of the sub-assembly body to mate with another SC connector inside a mating sleeve (also called adapter or coupler).

The connector housing - Connector sub-assembly body is then assembled together with the connector housing. Connector housing provides the mechanism for snapping into a mating sleeve (adapter) and hold the connector in place.

The fiber cable - Fiber cables are often crimped onto the connector sub-assembly body with a crimp eyelet. This provides the strength for mechanical handing of the connector without putting stress on the fiber itself.

The stress relief boot - Stress relief boot covers the joint between connector body and fiber cable, and protects fiber cable from mechanical damage.

SC Connector Types

According to the polish style, SC connector can be divided into PC (Physical Contact) style, UPC (Ultra Physical Contact) style and APC (Angled Physical Contact) style. SC PC connector is polished with a slight spherical (cone) design to reduce the overall size of the end-face. But now, the most common types are UPC type and APC type.

SC UPC connector - It is an improvement from SC PC connector, resulting in a lower back reflection (ORL) than a standard PC connector, and allowing more reliable signals in digital TV, telephony and data systems. It is available in single-mode and multimode. You can tell them apart from the color: SMF UPC connector is blue, while MMF UPC connector is beige.

SC APC connector - It is angled at an industry-standard eight degrees. As a result, any light that is redirected back towards the source is actually reflected out into the fiber cladding, again by virtue of the 8° angled end-face. That is why its back reflection is the lowest among the three types. APC connector is only available in single-mode, and the color of it is green.

According to the application, SC connector includes SC BTW connector and SC jumper connector.

SC BTW Connectors - BTW is the abbreviation of “behind the wall”. As the name implies, can be used to connect the adapter panel, and then terminate Outside Plant (OSP) cables as well as building cables. SC BTW connectors are designed for 900 micron buffered fiber. This product is intended to meet Telcordia GR-326-CORE, Issue 3 for Type II Media (900 micron buffered fiber).

SC Jumper Connectors - Generally, SC jumper connectors are designed on the end of fiber patch cables, and then connect GBIC modules in Central Office (CO), Local Area Networks (LANs), device terminations, etc. Robust family of connectors designed to mount on 1.6 – 3.0 mm fiber cordage and intended to meet the Telcordia GR-326-CORE, Issue 3, for Type I Media (reinforced jumper cordage). The common types are 2mm Jumper connector and 3mm Jumper connector.

SC Connector Application

Generally, when compared with other connectors, SC connector is more rugged and adaptable. What is more, it is capable of tunable and stable performance. With these significantly features, SC connector can be applied in many fields, such as telecommunication, CATV, broadband and so on. The products of SC connector are also various, such as SC adapters, SC terminators, SC converters and SC jumpers.

Fiberstore Solution

Fiberstore as the main professional fiber optic products manufacturer in china offers a various kinds of fiber cable connectors, including SC Connectors. What is more, the products with these connectors are also full in store, such as SC fiber cable, with good quality and low price.

Article Source: www.chinacablesbuy.com/

Guide to Optical Attenuators

Attenuators Overview

An optical attenuator, or fiber optic attenuator, is a device used to reduce the power level of an optical signal, either in free space or in an optical fiber. The optical attenuators can have a tuning control to set the level of attenuation into a range of selectable values (variable optical attenuators), or can introduce a fixed level of attenuation (fixed optical attenuators). 

Variable optical attenuators are normally used for testing and measurement. Also they could be used in EDFAs (erbium doped fiber amplifier) for equalizing the light power among separate channels. Fixed optical attenuators have fixed values specified in decibels. The attenuation is expressed in dB and its value cannot be varied. It is ideal for attenuating single-mode fiber connectors in various applications.

Why Use Optical Attenuators?

Optical attenuators is a critical component of any fiber optic network. Using an attenuator, the transmission signal into the dynamic range of the receiver could be adjusted. This increases the life span of the optical equipment and ultimately provides a clearer transmission signal. Moreover, the utilization of optical attenuators could assure the linear behaviour of optical fiber receivers avoiding optical power overloading. At the same time, it is able to balance the optical power into passive optical network branches and can make measurements on an optical telecommunication system.

How Optical Attenuators Work?

Optical attenuators usually work by absorbing the light, like sunglasses absorb the extra light energy. Typically, they have a working wavelength range in which they absorb the light energy equally. However, they should not reflect the light since that could cause unwanted back reflection in the fiber system. Another type of attenuator utilizes a length of high-loss optical fiber, that operates upon its input optical signal power level in such a way that its output signal power level is less than the input level.

Application of Optical Attenuators

Optical attenuators are commonly used in fiber optic communications. They could be used to test power level margins by temporarily adding a calibrated amount of signal loss, or installed permanently to properly match transmitter and receiver levels. 

One of the important applications of optical attenuators is channel balancing in WDMs (wavelength division multiplexing). As illustrated in the following picture, an eight channel wavelength multiplexed signal from a trunk line is demultiplexed into individual signals. The signals are of different intensities, and need to be balanced to avoid saturating any of the receivers. So each channel is sent through a corresponding port on an eight channel MEMS (micro-electro-mechanical systems) VOA (variable optical attenuator). The signal strength through the optical attenuator outputs is monitored by a control circuit. If the output signal gets too high or too low, the corresponding optical attenuator is adjusted to bring the light level to the correct range.

As stated above, an optical attenuator is used to reduce the power level when there is too much light deliver through a fiber optic receiver. It is used to adjust optical signal levels thereby increasing network flexibility and providing management of optical power. If you are looking for an optical attenuator, Fiberstore is a primary option. It has many different fixed optical attenuators and variable optical attenuators including fixed LC/APC fiber optic attenuator, fixed SC/UPC fiber optic attenuator, BVA610 optical variable attenuator(0-60dB), etc. For more information, you can visit www.fiberstore.com.

Originally published at www.fiber-optic-components.com/guide-to-optical-attenuators.html

50µm and 62.5µm Multimode Optical Fiber: Which Is More Preferable?

Multimode optical fiber is a type of optical fiber mainly used for transmission over short distances, such as in a building or on a campus. Typical multimode optical fibers support data rates from 10 Mbps to 10 Gbps over link lengths of up to 600 meters. It can offer reliable, flexible and cost effective cabling solutions for local area networks, central offices and data centers.

What Are 50/125µm and 62.5/125µm Multimode Optical Fiber?

According to the core and cladding diameters, multimode optical fiber can be divided into 50/125 µm and 62.5/125 µm. 50 µm and 62.5 µm refer to the diameters of the fiber core, which is the area that carries light signals. 125 µm means the cladding diameter of the fiber. The cladding confines the light to the core as it has a lower index of refraction. Cable construction is shown in the following diagram indicating the cable core, cladding and outer jacket diameters. Currently, there are four types of multimode optical fibers: 62.5µm multimode optical fiber (OM1), 50µm multimode optical fiber (OM2), laser-optimized 50µm multimode optical fiber (OM3) and laser-optimized 50µm multimode optical fiber (OM4). 

Why Two Core Diameters?

When optical fiber was introduced for 10Mbps and then 100Mbps Ethernet, light-emitting diode (LED) light sources and 62.5µm fiber were used. LEDs overfill the fiber core, so larger core diameters mean more light is collected, and thus data can be carried farther as shown in the following picture A. 

In order to achieve 1Gbps performance, the light source was upgraded to vertical-cavity surface-emitting laser (VCSEL). VCSELs can switch more rapidly than LEDS, which makes them better for higher data rates. Moreover, VCSELs emit much smaller and more sharply focused beams, coupling more power into the fiber for greater efficiency as the following picture B shown. With a VCSEL light source, all of the light is coupled into the fiber, so a larger core diameter does not gather more light. In fact, a larger core diameter transmits the light less efficiently as a result of modal dispersion. Using 50µm fiber decreased modal dispersion and then increased the reach of 1Gbps fiber cabling.

Which Is More Preferable?

62.5µm fiber could support 2km campuses at 10 Mbps because more light for LEDs could be coupled into its larger core. And it dominated the premises market for more than a decade. However, with faster transmission rates and higher bandwidth demands, changing market conditions was imperative. So 50µm fiber has been established as the best solution for applications > 10 Mbps. The 100Mbps Fast Ethernet standard invited the use of LEDs that take advantage of lower fiber attenuation at 1300nm wavelength, which offset the LED coupling loss into 50µm fiber caused by its smaller core diameter. Hence, 50µm fiber could support the same 2km reach at 100 Mbps as 62.5µm fiber.

As data rates rise to Gigabit speeds, 62.5µm fiber is stretched beyond its performance limit because of its lower bandwidth at 850 nm. By contrast, 50µm fiber has as much as ten times the bandwidth of the 62.5µm fiber, which enables support of 1Gbps and 10Gbps applications. As 1Gbps and 10Gbps transmitters use small spot-size lasers, concerns over power coupling efficiency into 50µm fiber are no longer an issue. Moreover, the laser-optimized 50µm multimode optical fiber can offer the most secure and least-cost upgrade path to higher-speed networks as it is able to support 40 and 100Gbps data transmission.

Conclusion

As stated above, 50µm multimode optical fiber is more preferable than 62.5µm multimode optical fiber. Using 50µm multimode optical fiber can bring benefits of faster transmission rates and higher bandwidth. If you have not put 50µm multimode optical fiber into use, it is time to employ 50µm multimode optical fiber for higher performance on your network.

Article source: www.fiber-optic-components.com/50%C2%B5m-and-62-5%C2%B5m-multimode-optical-fiber-which-is-more-preferable.html

Passive Optical Network–A Superior Network Solution

With the explosive growth of Internet, the introduction of a broadband access network based on fiber-to-the-office (FTTO) and fiber-to-the-home (FTTH) has been triggered. Under this circumstance, access and metro networks should be scalable in terms of capacity and accommodation as well as flexible with regard to physical topology. Passive optical network (PON), one class of fiber access system, can deal with the various demands.

Definition

A passive optical network (PON) is a telecommunication network that uses point-to-multipoint fiber to the end-points in which unpowered optical splitters are used to enable a single optical fiber to serve multiple end-points. It consists of an optical line terminal (OLT) at the service provider’s central office and a number of optical network units (ONUs) or optical network terminals (ONTs), near end users (see below figure). PON takes advantages of wavelength division multiplexing (WDM) and uses one optical wavelength for upstream traffic while another for downstream traffic on a single-mode fiber. The upstream signals are combined at the splitters by using a multiple access protocol (time division multiple access). The downstream signals are directed to multiple users by passive optical splitter technology.

Advantages

There are two ways that the signals can be broken out in shared fiber architectures. One is active Ethernet (AE), with which the individual signals are split out using electronic equipment near the subscriber. The other one is PON, in which the signals are replicated passively by the splitter. Compared with AE, a network based on a PON system is more superior. The advantages of PON are as below.

PON incurs lower capital expenditures because it has no electronic components in the field. Also PON lowers the operational expenditures as there is no need for the operators to provide and monitor electrical power in the field or maintain backup batteries. Besides, a PON has a higher reliability because in the PON outside plant there are no electronic components which are prone to failure. Additionally, one of the most crucial features of a PON-based access network is its signal rate and format transparency. It is much simpler for a PON to upgrade to higher bit rates. Both AE and PON require upgraded electronics in the CO and customer premises, but unlike AE, PON does not need to upgrade in the outside plant as the passive splitters are agnostic to PON speed. Lastly, a PON solution has the ability to span long distances without degrading performance. The low-loss characteristics of single-mode fiber enable PON to support a maximum physical reach of 20 kilometers.

Applications

There are some applications for which PON is well suited, such as fiber-to-the-home (FTTH) delivery of voice, Internet data, and cable access broadband video. More specifically, PON is used when the applications require anticipated system to upgrade to high-security areas or where the rerouting of cable may be difficult. Or in the cases that installations involving widely dispersed nodes require long runs of fiber. And PON is utilized for the projects where costs, especially initial deployment costs, are a key concern. At the same time, using PON can help user bandwidth to be adequately managed.

By reading the above illustration, have you got a basic understanding about the passive optical network? Fiberstore, a professional manufacturer and supplier in the optical industry, has many high-quality PON products including PON splitters, optical network units and optical line terminal. Choosing a PON product in Fiberstore can help to deploy your network more efficiently.

Originally published: www.fiber-optic-components.com/passive-optical-network-a-superior-network-solution.html