WDM Overview

With the development of the computers, mobile phones and some other things, there is an increasing eagerness for more traffic volume of telecommunication. So WDM, with more bandwidth and faster data transmission rate, comes into being.

WDM is a technology to send multiple different wavelength lasers on a single optical fiber. As shown in the picture below, there are different signals coming from different channels. when through the multiplexer, they can be transmitted on a single fiber without obstructed by each other at a high speed. And then, when they are through the demultiplexer, they will be allocated into different channels. The multiplexer and the demultiplexer are the most important parts in WDM systems, just like transmitter and receiver. When signals are transmitted to the network medium on the fiber links, they will be amplified. And after through the network medium, the signals will still be amplified on the fiber links untill they are received by the receiver.

Currently, there are two types of it in the market. CWDM, short for coarse wavelength division multiplexing, is a low-cost WDM transmission technology. Another type is DWDM, namely, dense wavelength division multiplexing. The primary difference between them is the channel spacing. The channel spacing of CWDM is wider than DWDM, so that the number of its channels on the same link could be reduced relatively. As a result, its optical interface components does not need to be precise as same as DWDM.

Now the technology of WDM is widely used in optical networks. Why can it be so widely used? The reasons is closely linked to its features. First, it has Super capacity transmission technology. The transmission capacity can be up to 300-400 Gbit/s or even larger. Second, it can save fiber resources. No matter how many SDH subsystems there are, the whole reuse system only needs a pair of optical fiber. Third, it can work with EDFA that strengthens and restores the attenuated signals in the long-distance transmission, so that it can reduce the cost. Forth, it can improve the reliability of the system. Because most WDM systems are the photoelectric devices which have high reliability. This is a guarantee for the system reliability.

As the optical communication technology progressed further, WDM will be developed in some aspects. In terms of DWDM, Something still needs to be improved such as cost, so that more customers can adopt it.

Originally published at http://www.chinacablesbuy.com/wdm-overview-3.html

How to Classify Fiber Optic Patch Cords?

Nowadays, fiber optic patch cords are widely used in the telecommunication room, local area network, optical fiber communication system or other devices. They are the cables that connect the devices and the fiber optic cabling link, generally applied into connecting the optical transceivers and the terminal boxes. They have a thick layer for protection. Fiber optical patch cords are the similar to the coaxial cable, but they don’t have a mesh shield. The glass core of light propagation is in the center.

Fristly, according to their transmission medium, fiber optic patch cords suppliers often provide two types of them. They are singlemode fiber and mutimode fiber. The core diameter of mutimode fiber is 50μm ~ 65μm, as thin as the human’s hair. Mutimode fiber is often in yellow, and its connector and protective case are usually in blue. Singlemode fiber’s core diameter is 8μm~10μm. It is often in orange or sometimes in gray, and they usually use the beige or black connector and protective case. In the part of transmission distance, mutimode fiber is applied in the short transmission distance, while the singlemode fiber is applied in the long transmission distance.

Fiber Optic Patch Cord

Secondly, according to their connector form structure, fiber optic patch cords suppliers can offer various kinds, such as FC jumper, SC Jumper, ST Jumper, LC jumper, MTRJ jumper, MPO jumper and so on. Now the commonly used fiber optic patch cords are FC, SC, ST and LC jumpers.

• FC jumper generally is adopted on ODF side, using a metal sleeve to reinforce its external surface, and the turnbuckle to fasten itself.
• SC jumper, it has rectangular shell, using the latch type to fasten, and do not need rotation. It is mostly used on the router switch.
• ST jumper is commonly used in fiber optic patch panels with the turnbuckle fastened. It has rounded shell. Commonly, it is used in optical fiber distribution frame.
• LC jumper is made by the RJ latch mechanism which is operated easily, commonly used on the routers.

What is more, according to the material of their outer sheath, fiber optic patch cords suppliers can offer four types. They are ordinary jumper, common flame jumper, low smoke zero halogen jumper and halogen flame jumper. The point common flame jumper different from the ordinary jumper is that the insulator of common flame jumper won’t burn when it is in the high temperature. Relatively, it is safer than ordinary jumper. Low smoke zero halogen jumper is the environmentally friendly jumper that means it has non-halogen such as F, Cl, Br and I, and also does not contain Pb, Cd, Cr and Hg. In the case of combustion, it can’t release halogen-containing gases, and the smoke density is very low. And halogen flame jumper has all the advantages of low smoke zero halogen jumper. In addition, it has another advantage that in the high temperature its insulator won’t burn. This advantage is as same as common flame jumper. After a comprehensive comparison, the halogen flame jumper could be the bestseller.

Recently, there are more and more fiber optic patch cords suppliers so that it is more convenient for customers to buy the fiber optic patch cords. If you don’t know what kind of patch cords you should buy, just follow the above classifications.

Classification of Gigabit Ethernet SFP Modules

Since the IEEE 802.3ae standard was approved in mid-year of 2002, the sales volume of Gigabit Ethernet ports has increased from hundreds of ports to tens of thousands of ports per quarter.
The specifications of Gigabit Ethernet can be divided into three types. One of these types is the fiber-based Gigabit Ethernet LAN specification. And the fiber-based Gigabit Ethernet LAN specification has six types. They are 10GBase-SR, 10GBase-LR, 10GBase-LRM, 10GBase-ER, 10GBase-ZR and 10GBase-LX4. They all can be applied into the SFP modules.
10GBASE-SR SFP Module
10GBASE-SR is defined by the standard of IEEE 802.11ae. 10GBASE-SR is one of the six kinds of specifications for 10GbE LAN (regional communications network) series. It transmits over multimode optical fiber, allowing the light with a wavelength of 850 nm to transmit at 300 m distance. The “SR” stands for “short range”. Its transmission rate is 10.3124Gbps. Because of the coding using the 64B / 66B mode, the actual data transfer speed is 10Gbps. 10GBase-SR SFP modules are the smallest fiber modules, having the advantages of the lowest cost, lowest power consumption.

10GBASE-LX4 SFP Module
With the technology of WDM, 10GBase-LX4 works in 3.125Gb/s separate light source to achieve 10Gb / s transmission by using four wavelengths unified as 1300 nm. The transmission distance in mutimode fiber is 2 ~ 300 m, while in singlemode fiber, the effective transmission distance is up to 10km. It is mainly used in the environment which supports both multimode and singlemode fiber.
10GBASE-LR SFP Module
The “LR” in the 10GBase-LR SFP modules stands for “Long Range”. 10GBase-LR can support longwave (1310 nm) singlemode fiber encoded with 64B/66B. Its effective transmission distance is from 2 m to 10 km. And the longest transmission distance can be up to 25 km. What is more, 10GBase-LR SFP modules is cheaper than 10GBase-LX4 SFP modules.
10GBASE-LRM SFP Module
The “LRM” stands for “Long Reach Multimode”. Its effective transmission distance is about 220 m, and can be up to 260 m in OM3 fiber. Compared with 10GBASE-LX4 SFP module, it has lower cost and lower power consumption.
10GBASE-ER SFP Module
“ER” in the 10GBase-ER SFP module stands for “Extended Range”. It can support long wave (1550 nm) singlemode fiber, and the effective transmission distance is about 2 m to 40 km.
10GBASE-ZR SFP Module
10GBase-ZR SFP module can support long wave (1550 nm) singlemode fiber, and the effective transmission distance is up to 80 km. It is not covered by IEEE 802.3ae, but defined by OC-192/STM-64 SDH/SONET.

The Development of 100G CFP Optical Transceiver

With the rapid development of Internet, mobile Internet and networking, the customers’ business needs are continuing expanding. As a result, data traffic keeps rising. 100G transceiver currently carries most of the network traffic. It is not exaggerating to say that 100G transceiver is the inevitable trend of the market. 100G transceiver offers 100 Gigabit Ethernet connectivity options for data center networking to customers. It is of great significance to the enterprise core aggregation, and services provider transport applications. The interface of the 100G transceiver is connected with CFP module. CFP, short for C form-factor pluggable, whose standard is mainly to develop for 100 Gigabit Ethernet systems, is hot-pluggable transceiver that supports a wide range of 40 and 100 Gb/s applications, including next-generation high speed Ethernet (40GbE and 100GbE). 

Compared with CFP module, the volume of CFP2 optical transceiver is smaller, only half the size of it. In addition, CFP2 optical transceiver provides users the same data rate as CFP module at up to a third of the power, reducing overall power consumption. CFP2 module is a new technology. From OFC in 2013, a lot of companies have introduced related products. Now CFP2 module has a wide range of applications in the field of data, communication, storage network, and even the popular current cloud computing. So in the next few years, CFP2 module will have a large application prospects and space.

CFP2 optical transceiver

Last year, CFP4 optical transceiver module came along. Its volume is even smaller than CFP2 module’s. The volume of CFP4 optical transceiver module is half of CFP2 module, a quarter of CFP module. And its power consumption declines sharply, so that it is more attractive in the new ultra-high-bandwidth data center and core routers field. Network equipment manufacturers can migrate from CFP2 to CFP4 interface, making the density of the front panel port doubled. 

But the problem is that the technology of CFP4 module is not very mature. A certain time still should be required. So for CFP2 module, it will have a certain application space, probably continuing for 2 years. On the other hand, if the equipment manufacturers still do not think about entering the core router market, then CFP module and CFP2 module can be enough to meet users’ needs. This status would be benefit for cost control and user procurement in that CFP module and CFP2 module are much cheaper than CFP4.

What Is Mutimode Fiber Patch Cable?

Mutimode fiber patch cable is one of the types of the fiber patch cable. Fiber optic patch cable, consisting of a short length of optical fiber with a connector on either end, is the simplest fiber optic components. Multimode fiber optic transmits mutimode on a given operating wavelength. The numerical aperture of the ordinary multimode optical fiber is 0.2 ± 0.02. Multimode fiber transmits hundreds of modes, and the propagation constant and the group rate of each mode are different. Since its signals will be weakened with the increase of the distance, it is suitable for short-distance optical fiber communication systems and small capacity.
 
Differences From Singlemode Fiber Patch Cable
Fiber patch cable has two types: mutimode fiber patch cable and singlemode fiber patch cable. So how can we tell them apart? The size of their respective cores is the main difference between singlemode and multimode fiber patch cables. Multimode fibers have a much larger core than single-mode (50, 62.5 mm or even higher), while singlemode cables only have a core of 8 to 10 microns. This advantages allows light transmission can go through more different paths. The larger core gathers more light in multimode fiber patch cables than singlemode cables, and this light reflects off the core and allows more signals to be transmitted. On the other hand, single modes fiber enables lights to be transported in a single wavelength, allowing the singles to travel faster in longer distances without little signal loss.
Types of Mutimode Fiber Patch Cables
According to its refractive index distribution, mutimode fiber patch cables are divided into two types. One is step index multimode fiber. Another is graded mutimode fiber. Step index multimode fiber is mostly used as “light guide” for instrumentation purposes. Its core diameter is large, about 100 to1500 µm. It has large NA (0.22, 0.29, 0.37, 0.43, …) , low-OH (for IR) and high-OH (for UV) versions. Graded index multimode fiber is mostly used as “digital” fiber for LAN application. Compared to step index fibers, graded refraction index fibers can transmit data at max rate for it reduces pluse dispersion. Its high bit rate over short distances is about 10Gbps within 550m. Its medium size core diameter is about 50µm (OM2 and OM3) , and the typical wavelengths are 850 and 1310 nm. Compared to the graded mutiomode fiber, step index multimode fiber have lower bandwidth. When it is applicated in the web, the fiber, whose fiber core diameter is 62.5μm, and the cladding diameter is 125μm, is the most popular multimode fiber.

Essential Information About SFP Modules

Introduction of SFP Modules

SFP, short for Small Form-factor Pluggable, is a compact optical transceiver module used in optical communications. SFP optical transceivers are hot-swappable, compact media connectors that provide instant fiber connectivity for your networking gear. They are an effective way to connect a single network device to a wide variety of fiber cable distances and types. SFP optical module is mainly composed by laser TOSA (including the transmitter and receiver, ROSA), circuit board IC and other external accessories. It is expected to perform at data speeds of up to five gigabits per second (5 Gbps), and possibly higher. Because SFP modules can be easily interchanged, electro-optical or fiber optic networks can be upgraded and maintained more conveniently than has been the case with traditional soldered-in modules.

The types of SFP Modules

SFP transceivers are able to provide an excellent amount of variation to consumers. They have a various different transmitters and receivers types, allowing users to decide on the appropriate SFP transceiver for each link to offer the required optical reach.Optical SFP modules are commonly available in two different categories:

Fiber SFP

Fiber SFPs contain only the laser driver, photodiode receiver and some simple AGC logic. Whatever comes to the LVDS input of such an SFP, goes out to the fiber preserving exactly the same protocol and timing (+/- the jitter).
For multimode fiber, with black or beige extraction lever
There is SX-850nm, for a maximum of 550m at 1.25Gbit/s (gigabit Ethernet) or 150m at 4.25Gbit/s (Fibre Channel)
For singlemode fiber, with blue extraction lever
There is LX-1310nm (for distances up to 10km), EX-1310nm (for distances up to 40km) and ZX-1550nm (for distances up to 80km, with green extraction lever)

Copper SFP

Copper SFPs are deigned to be used in copper networks. Copper SFPs are on the other hand, not only transceivers. They convert the 8b10b protocol used in 1000Base-X (SFP interface) to a much more complex 1000Base-T physical layer protocol. Driving a CAT5/6 copper directly with 1.25 GBaud signal as in 1000Base-X is not possible.
For copper twisted pair cabling
1000BASE-T- these modules incorporate significant interface circuitry and can only be used for gigabit Ethernet, as that is the interface they implement. They are not compatible with (or rather: do not have equivalents for) Fiber channel or SONET.

Benefits of SFP Modules

SFP Transceiver Module is also hot pluggable, which make it easy to change and easy for maintenance compared with traditional modules. Meanwhile, they are compatible to multiple setups across both fiber optic and copper channels. When you need long or short distance communication, SFP transceivers play an important role in that.
SFP Transceiver Module is regarded as the upgrade version GBIC, unlike GBIC, SFP Transceiver Module saving more space, and it interfaces a network device mother board (for a router, switch, media converter or similar device) to a fiber optic or copper networking cable. It is a popular industry format supported by many network component vendors.
SFP transceivers module are designed to support SONET, Gigabit Ethernet, Fiber Channel, and other communications standards. SFP transceiver modules make the fiber optic network or fiber-Ethernet network easier to upgrade or maintain users to replace a single SFP module during the process, rather than replace the whole board with many modules on it.

Multimode Fiber Overview

What Is Multimode Fiber?
Multimode fiber is a kind of optical fiber designed to transport multiple light rays or modes concurrently which are reflected at slightly distinct angles within the optical fiber core. It can typically transmit signals at rates of 10 Mbit/s to 10 Gbit/s over link lengths of up to 600 meters (2000 feet). It is widely used for communication over short distances, such as within a building or on a campus.

What Makes Mutimode Fiber Different
There are various differences between multimode fiber and singlemode fiber. Of all them, the size of the "core" plays the most important role in making multimode fiber distinct from singlemode fiber. Signlemode fiber uses a very thin core which isolates the laser to a single beam, but multimode fiber use a relatively thicker core which allows it to reflect back and forth within the core, having several beams be sent at once. This enables multimode fiber to transmit data at higher rates than singlemode fiber, because the larger core simply can allows more light to be transported simultaneously. It is understood that more light means more data.

What Is Mulimode Fiber Used for？
The equipment used for optical communications over multimode is less expensive than that for singlemode fiber. And due to its other advantages like high capacity and reliablity, multimode fiber is generally used for a backbone. A growing number of users benefits from running fiber to the desktop or to the zone. Standards-compliant architectures such as Centralized Cabling and fiber to the telecom enclosure (FTTE) enable users leverage the distance capabilities of fiber by centralizing electronics in telecommunications rooms, rather than having active electronics on each floor.

Types of Multimode Fiber 
Multimode fiber can be classified into different types by two standards. By their core and cladding diameters, multimode fibers can be divided into two types called step-index fibers and graded-index fibers. The refractive index of graded-index fibers decreases steadily as the distances from fiber axis extends. But the refractive index of step-index fibers decreases dramatically between the core and the cladding. And by the ISO 11801 standard, multimode fibers can be divided into four types called OM1, OM2, OM3, and OM4 which is based on their modal bandwidth. Here is a brief introduction of them.