How to Understand DDM/DOM Function of SFP Transceiver

When seeing the parameters of SFP transceivers, have you ever been confused about the description of “DDM/DOM support”? Definitely, the SFP transceivers with this supported function are better than those transceivers without such function. What is the real meaning of this parameter and how do we use it to facilitate our work? This article will give you the detailed answers.

What Does DDM/DOM Mean?

DDM refers to Digital Diagnostics Monitoring. It is a technology used in SFP transceivers which gives the end user the ability to monitor real-time parameters of the transceivers. The monitored parameters include optical output power, optical input power, temperature, laser bias current, and transceiver supply voltage etc.

DOM refers to Digital Optical Monitoring. It is also a technology which allows you to monitor important parameters of the transceiver module in real-time. You can use DOM to monitor the TX (transmit) and RX (receive) ports of the module, as well as input/output power, temperature, and voltage. According to these monitored parameters, network technicians are able to check and ensure that the module is functioning well.

Typically, DDM and DOM are similar to each other. They are usually used together to describe the real-time monitoring function of SFP transceivers.

Three Applications of DDM/DOM

Predicting Module Lifespan

This failure prediction enables network managers to find potential link failures before the system performance is affected. Through fault tracing, the network administrator can switch services to the backup link or replace the suspicious device in order to repair the system without interruption. By the real-time monitoring of operating voltage and temperature inside the SFP transceiver, administrators can identify the potential problems. For example, when Vcc voltage is too high, it will cause the breakdown of CMOS device, but when it is too low, the laser will be unable to work.

Locating Fault Position

In an optical link, locating the location of a fault is critical to the rapid loading of service. The fault isolation feature of DDM/DOM allows the system administrator to quickly locate the link failure. It can be used to locate whether the fault is in the module or on the line, and whether the fault is in the local module or in the remote module. By quickly locating the fault, the fault recovery time of the system is greatly reduced.

Verifying Module Compatibility

Another application of DDM/DOM is the verification of module compatibility. Compatibility verification is used to analyze if module's working environment is consistent with the data sheet or compatible with the relevant standards or not. The performance of the module can only be guaranteed in the compatible working environment. Otherwise, the non-compatible environment will cause the decreased performance of transceivers, resulting in transmission error.

How to Use DDM/DOM?

Here are five steps of executing the DDM/DOM commands in SFP transceivers:

Step one, Enable example: Router> enable (Enables the privileged EXEC mode. Enter your password if prompted.)

Step two, Configure terminal example: Router#configure terminal (Enters the global configuration mode.)

Step three, Transceiver type all example: Router (config) #transceiver type all (Enters the transceiver type configuration mode.)

Step four, Monitoring example: Router (config-xcvr-type) #monitoring (Enables monitoring of all optical transceivers.)

Step five, Monitoring interval example: Router (config-xcvr-type) #monitoring interval 500 ((Optional) Specifies the time interval for monitoring optical transceivers. Valid range is 300 to 3600 seconds, and the default value is 600 seconds.)

Conclusion

From this article, you can know that DDM/DOM function assists the network specialists easily find out problems inside fiber links. It simplifies the maintenance work and secures the system’s reliability. We provide many types of SFP transceivers with DDM/DOM function. If you have such requirement for your device, please search at our website for more information.

source:http://www.sfp-transceiver-modules.com/wiki/a/117/How-to-Understand-DDM/DOM-Function-of-SFP-Transceiver

Commonly Used SFP Transceivers

In fiber optic networking, an optical transceiver is a device which can both transmit or receive light and electrical signals. Generally, it has two ports. One is the transmitting port used for converting electrical signal into light signal and the other is the receiving port used for changing light signal into electrical signal. According to different data rates, there are many different kinds of transceivers, such as small form-factor pluggable (SFP), small form-factor pluggable plus (SFP+), quad small form-factor pluggable plus (QSFP+), centum form-factor pluggable (CFP), etc. And this article is going to give a brief introduction to some commonly used SFP transceivers. SFP transceiver, known as small form-factor pluggable transceiver, is a compact and hot-pluggable transceiver used for both telecommunication and data communication applications. It is widely deployed for the Fast Ethernet and Gigabit Ethernet.

Here are some commonly used SFP transceivers:

BiDi SFP

BiDi SFP is short for Bi-Directional SFP. The core technology of this transceiver is the BiDi technique which enables bidirectional transmission of two different waves. Since the BiDi module has only one port , it must be deployed in pairs. For example, when one module is used for receiving 1310nm and transmitting 1550nm optical signals, the other should receive 1550nm and transmit 1310nm signals, and vice versa. In this way, BiDi transceivers usually cost twice the price of other transceivers, but it is a better way to use BiDi transceivers to save the expenditure spent on optical fiber. Because BiDi transceivers have the advantage of reducing fiber cabling infrastructure costs by lowering the number of fiber patch panel ports, decreasing the amount of tray space dedicated to fiber management, and using less fiber cable.

CWDM SFP

CWDM SFP is a kind of single-mode transceiver used for Gigabit Ethernet and Fibre Channel applications. It is made up of three parts: an uncooled laser transmitter, a PIN photodiode integrated with a trans-impedance preamplifier and a MCU control unit. The technology of this transceiver is called coarse wavelength-division multiplexing (CWDM). It is an economical technique to save fiber resources through transmitting multiple wavelengths on one optic fiber. The wavelengths of CWDM SFP are between 1470nm and 1610nm distinguished by different colors. Most commonly used CWDM SFP transceivers include CWDM SFP 1470, CWDM SFP 1490, CWDM SFP 1510, CWDM SFP 1530, CWDM SFP 1550, CWDM SFP 1570, CWDM SFP 1590, CWDM SFP 1610, etc. CWDM SFP can support the high performance of 1.25Gbps data rate and 80km distance of signal transmission.

DWDM SFP

Dense wavelength division multiplexing (DWDM) SFP is the hot-pluggable transceiver used for Gigabit Ethernet which gathers different wavelengths onto one single fiber. Compared with CWDM SFP, DWDM SFP has a more intensive wave spacing for a high performance of data communication. The working wavelength ranges from 1525 nm to 1565 nm or 1570 nm to 1610 nm. The wave intervals are varied in 0.4 nm, 0.8 nm, 1.6 nm, etc. And the port of this transceiver is using the SFP interface for over 1 gigabit optical data transmission.

SONET/SDH SFP

Synchronous optical networking (SONET) SFP or synchronous digital hierarchy (SDH) SFP is a kind of transceiver based on the SONET/SDH standard. SONET/SDH is the physical standard for fiber optical transmission, first brought out by Bellcore in 1980s and then standardized by American National Standards Institute (ANSI) for popularization all over the world. In the SONET/SDH standard, it mainly stipulates the transmission rate, fiber interface, operation and maintenance in optical fiber transmission. The SONET/SDH SFP transceivers can support OC-3 (up to 155.52 Mbps), OC-12 (up to 622.08 Mbps), and OC-48 (up to 2488.32 Mbps) data rates for multimode, short-reach, intermediate-reach, and long-reach applications. With the help of SONET/SDH technique, optical devices around the world are available to connect with each other which greatly improve the efficiency of data communication.

FC SFP

Fibre Channel (FC) SFP is a kind of transceiver using the technology of fiber channel for high speed optical signal transmission with a data rate up to 4.25 Gbps. Fiber channel is a mature technology for serial interface standardized by American National Standards Institute (ANSI). It is applied to the connection between the storage controller and computer drivers. Nowadays, FC has played as a replacement for the Small Computer System Interface (SCSI) in high-performance storage systems, because fiber channel is faster in transmission speed and more flexible in the transmitting mode with or without fiber in accordance with the transmission range.

Application

SFP sockets are found in Ethernet switches, routers, firewalls and network interface cards. In addition, storage interface cards, also called as HBAs or Fibre Channel storage switches, use the SFP modules to support different speeds such as 2Gb, 4Gb, and 8Gb. Because of the low cost, low profile, and ability to provide a connection to different types of optical fiber, SFP provides the related equipment with enhanced flexibility.

Conclusion

SFP transceivers are hot-pluggable small form factors used for 100BASE and 1000BASE Ethernet data transmission. There are different types of SFP modules, including BiDi SFP, CWDM SFP, DWDM SFP, SONET/SDH SFP and FC SFP. Each of them supports different techniques which bring convenience to data communication. FS.COM provides all the SFP transceivers mentioned above, the products will definitely meet your requirements.

The article originates from http://www.sfp-transceiver-modules.com/wiki/a/106/Commonly-Used-SFP-Transceivers.

Reasons for Choosing Optic Fiber Over Copper Cable

 Nowadays, facilities like studios and control rooms are being upgraded to support the 4G or even 5G networks. This calls for fiber-based infrastructures to support the higher data rates. Optic fiber can provide substantial advantages of high performance over longer distances, virtually unlimited bandwidth, reduced sensitivity to electrical interference, lower cost and design of greater space and lighter weight. These benefits make optic fiber much better than the average copper cable. Followings are some specifically explanatory reasons for choosing optic fiber over copper cable.

 Firstly, the virtually unlimited bandwidth of optical fiber is better than the bandwidth limit of copper coaxial cable (coax). With a relatively low attenuation, the unlimited bandwidth is able to produce some rather surprising increases in capacity and range. Here’s an example, some fiber optic product combinations can reach the link length of more than 100km while a copper cable can only handle 3G for up to 75m. It can also carry multiple signals and a wide range of signal formats in a single cable. Moreover, the virtually unlimited bandwidth makes it possible for optic fibers to transmit bidirectional wavelengths with one in the forward direction and another in the reverse direction. 

 Secondly, the cost of fiber is not that expensive as it was before. In general, fiber cable is more expensive than copper cable in the short run, but it may be less expensive in the long run. The typical published price in the US for a single core PVC jacketed single-mode fiber is even cheaper than broadcast quality coax cable, suitable for HD-SDI, thus it is not a dream to make the cost of other optic fibers less than the cost of copper cable in the future. When transmitting the different signal types of digital systems, for instance, two video signals with four channels of audio, this benefit is required to make the digital systems affordable for people. In a word, bandwidth costs money, and fiber offers a way to minimize these costs. 

 Thirdly, the design of size and weight of the optic fiber is better than the copper cable. For example, a 2.9mm single core fiber weighs about 9 grams per meter, but a 1694A coax is about 61 grams per meter which is over six and a half times heavier than optic fiber. This kind of advantage is especially benefit for production trucks or OB vans which can solve the tight space and weight problems.

 From the discussion above, we may have a general understanding of why we should choose optic fiber rather than copper cable. In addition, there are also some ways for easier fiber transition. 

 One is the using of Small Form-factor Pluggable (SFP) fiber optic transceiver. SFP fiber modules are small, hot-pluggable devices used to provide fiber connectivity to 3G/HD/SD devices. The single-mode SFP fiber optic transceiver helps devices to be used over long range without degrading signal quality. The most important benefit is that SFP simplifies the migration to fiber. 

 Another method is the utilizing of CWDM fiber. It is ideally used to meet the demand of carrying multiple and different signals across long distances, either building-to-building or truck-to-truck. The CWDM MUX unit can combine at most 18 different wavelengths into a single optical fiber, and it is the same for CWDM DEMUX in reverse. Signal types are irrelevant to these units, thus different signals like AES, MADI, DVB-ASI, 3G/HD/SD-SDI or Ethernet can travel on the same fiber link. 

 To sum up, the benefits of choosing optic fiber are more than choosing copper cable. Because fiber cable costs less than it was once, becomes physically smaller, and weighs less. Also, compared to one copper coax, a single fiber is available to carry 18 full 3G signals, and a fiber signal path can be 500 to 1000 times longer than that of copper coax. From a system design, installation and maintenance perspective, the application of SFP fiber and CWDM fiber also helps a simpler proposition for optic fiber cable. Hence, optic fiber is highly recommended to be used in all broadcast facilities, as well as at pay TV operator networks. Optic fiber is a better choice for everyone.

FC SFP

Fiber Channel (FC) SFP is the transceiver using the technology of fiber channel for the high speed optical signal transmission. Fiber channel is a mature technology for serial interface standardized by American National Standards Institute (ANSI), it is applied for the connection between the storage controller and computer drivers. Nowadays, FC has played as a replacement for the Small Computer System Interface (SCSI) in high-performance storage systems, because fiber channel is faster in transmission speed, and more flexible in the transmitting mode with or without fiber in accordance with the transmission range.

SONET SFP

Synchronous Optical Networking (SONET) SFP or Synchronous Digital Hierarchy (SDH) SFP is a kind of transceiver based on the SONET/SDH standard. SONET is the physical standard for fiber optical transmission, first brought out by Bellcore in 1980s and then standardized by American National Standards Institute (ANSI) for the popularization in the whole world. In the SONET standard, it mainly stipulates the transmission rate, fiber interface, operation and maintenance in optical fiber transmission. With the help of SONET, the communication device around the world can connect with each other, which greatly improved the efficiency of fiber communication.

DWDM SFP

Dense Wavelength Division Multiplexing Small Form-factor Pluggable (DWDM SFP) is the hot-pluggable transceiver used for Gigabit Ethernet which gathers different wavelengths together onto one single fiber. DWDM SFP has a more intensive wave spacing for a high performance of data communication, nowadays it can reach the speed up to 400Gbps on one optic fiber. The wave intervals are varied in 0.4nm, 0.8nm, 1.6nm etc. according to people’s need. The port of this transceiver still used the SFP interface for over 1 gigabit optical data transmission.

CWDM SFP

CWDM SFP is a kind of single mode transceiver used for Gigabit Ethernet and fiber channel applications. It is made up of three parts: a uncooled laser transmitter, a PIN photodiode integrated with a trans-impedance preamplifier and a MCU control unit. The wavelengths of CWDM SFP are between 1470nm and 1610nm distinguished by different colors. Most commonly used CWDM SFP transceivers include CWDM SFP 1470, CWDM SFP 1490, CWDM SFP 1510, CWDM SFP 1530, CWDM SFP 1550, CWDM SFP 1570, CWDM SFP 1590, CWDM SFP 1610. CWDM SFP can support the high performance of 1.25Gbps data rate and 80km distance of signal transmission.

BiDi SFP

BiDi SFP, known as Bi-Directional SFP, is the fiber optic transceiver for over 1 gigabit data transmission. The core technology of this kind of transceiver is BiDi transmission which uses Wavelength Division Multiplexing (WDM) technique for bidirectional transmission of two different waves with only one optical fiber. Since the BiDi module just has one port , it must be employed in pairs. For example, when one port is used for receiving 1310nm and transmitting 1550nm optical signals, the other should receive 1550nm and transmit 1310nm signals, and vice versa. In this way, BiDi products usually cost more money than ordinary ones, but it is a better way to use BiDi transceivers to save the optical fiber expenditure.

SFP Transceiver

SFP is a type of fiber optic transceiver used for the conversion of light and electricity signals, it is the abbreviation of small form-factor pluggable. SFP is a mini version of GBIC, it has all the functions of GBIC, for example, SFP can also transmit over 1 gigabit signals and it is hot-pluggable. The advantage of this transceiver is its small size which is easier for people to carry and install. SFP came into being in 2001 right after GBIC, it lead people to a smaller-sized era of fiber optic transceiver.