Tag Archives: fiber optic transceiver

What Limits the Optical Transmission Distance

Fiber optic network is gradually replacing copper network, because of its various advantages, like high speed, high density and high bandwidth, etc. Among which is that fiber optic cable can support much further distance than that of traditional copper cables like coax cable or twisted pair wire. However, in practice, the exact distance that fiber optic can support are limited by many factors. Transmission distance has become one of the biggest problems in the super fast optical communication. On one hand, with the expansion of the fiber optic network, distances for the optical links span meters to hundreds of meters and even kilometers. On the other hand, optical signal becomes weak over long distance. Stuck in this dilemma, many components and methods are being used to break the limitation of the transmission distance. This article will focus on the main factors that limit optical transmission distance.

Fiber Optic Cable Type

Generally, the maximum transmission distance is limited by dispersion in fiber optic cable. There are two types of dispersion that can affect the optical transmission distance. One is chromatic dispersion, which is the spreading of the signal over time resulting from the different speeds of light rays. The other is modal dispersion representing the spreading of the signal over time resulting from the different propagation mode.

Multimode transmission is largely affected by the modal dispersion, because of the fiber imperfections, these optical signals cannot arrive simultaneously and there is a delay between the fastest and the slowest modes, which causes the dispersion and limits the performance of multimode fiber. (shown in the following picture) For single-mode fiber, it is not model dispersion but chromatic dispersion that affects the transmission distance. This is because, the core of the single-mode fiber optic is much smaller than that of multimode fiber. That’s the main reason why single-mode can transmit signals over longer distance than multimode fiber.

modular dispersion

Light Source of Fiber Optic Transceiver

Fiber optic cable is the path sending the optical signals. However, most of the terminals are electronic based. The conversions between electrical signals and optical signals are necessary. This process is largely depending on fiber optic transceivers which are used in most of today’s fiber optic network. The conversion of signals is largely depend on a LED (light emitting diode) or a laser diode inside the transceiver, which is the light source of fiber optic transceiver. The light source can also affect the transmission distance of a fiber optic link.

LED diode based transceivers can only support short distances and low data rate transmission. Thus they cannot satisfy the increasing demand for higher data rate and longer transmission distance. For longer and higher transmission data rate, laser diode are used in most of the modern transceivers. The most commonly used laser sources in transceivers are Fabry Perot (FP) laser, Distributed Feedback (DFB) laser and Vertical-Cavity Surface-Emitting (VCSEL) laser. The following chart shows the main characteristics of these light sources.

Light Sources of Fiber Optic Transceivers
Light Source LED FP DFB VCSEL
Transmission Distance Short Range Medium Range Long Range Medium Range
Transmission Speed Low Speed High Speed Very High Speed High Speed
Transmission Frequency Wide Spectral width Medium Spectral Width Narrow Spectral Width Narrow Spectral Width
Cost Low Cost Moderate Cost High Cost Low Cost

 

Frequency of Transmission

As the above chart mentioned, different laser source supports different frequency. The maximum distance a fiber optic transmission system can support is affected by the frequency at which the fiber optic signal will be transmitted. Generally the higher the frequency, the greater distance the optical system can support. Thus, choosing the right frequency to transmit optical signals is necessary. Generally, multimode fiber cable uses frequencies of 850 nm and 1300 nm, and 1300nm and 1550 nm are standard for single-mode system.

Bandwidth

The bandwidth that fiber optic cable supports is another important factor that influences the transmission distance. In most case the transmission distance decreases proportionally, as the bandwidth increases. For instance, a fiber that can support 500 MHz bandwidth at a distance of one kilometer will only be able to support 250 MHz at 2 kilometers and 100 MHz at 5 kilometers. Due to the way in which light passes through them, single-mode fiber has an inherently higher bandwidth than multimode fiber.

Splices and Connectors

Splices or connectors in most fiber optic system are inevitable. Signal loss can be caused when the optical signal passes through each splice or connector. The amount of the loss depends on the types, quality and number of connectors and splices.

As a conclusion, the optical transmission distance is affected by a variety of factors, like fiber optic cable type, light source of transceiver, frequency of transmission, bandwidth that the network supported, splices and connectors. During the deployment of fiber optic network, the above mentioned factors should be considered to minimum the limitations on the transmission distance. Meanwhile, components like repeater and optical amplifiers are also useful to support the long distance transmission. To break the barriers that limit the transmission distance, there is still a long way to go.

Source: http://www.fs.com/blog/what-limits-the-optical-transmission-distance.html

What’s the Difference Between Transceiver & Transponder?

In a fiber optic communication network, there are many equipment and facilities to support the normal operation of the system. Fiber optic transponder and fiber optic transceiver are the one of these devices. Literally, both of them are with a prefix “trans”. It seems to imply that there is a similarity between them. Actually, they are not the same. So, what’s the difference between them, something difference on principle or applications? Today, we are going to have a discussion on this topic.

First, in order to better understand the difference between a fiber optic transceiver and a fiber optic transponder, we need to define what each one does.

Fiber Optic Transceiver
Most systems use a “transceiver” which includes both transmission and receiver in a single module. Its purpose, in broad terms, is to transmit and receive data. In fiber optic communication, the commonly used transceiver modules are hot-swappable I/O (input/output) devices which plug into module sockets. The transceiver acts to connect the electrical circuitry of the module with the optical or copper network. Devices such as routers or network interface cards provide one or more transceiver module slot (e.g GBIC, SFP, XFP), into which you can insert a transceiver module which is appropriate for that connection. The optical fiber, or wire, plugs into a connector on the transceiver module. There are multiple types of transceiver module available for use with different types of wire, fiber, different wavelengths within a fiber, and for communication over different distances. The most commonly used fiber optic transceivers include GBIC, SFP, SFP+, XFP, CFP, QSFP etc. They are widely used for different application, eg. 10G, 40G fiber optic transmission.

Fiber Optic Transponder
“Transponder” includes a transmitter and a responder. It is a similar device with transceiver. In optical fiber communications, a transponder is the element that sends and receives the optical signal from a fiber. A transponder is typically characterized by its data rate and the maximum distance the signal can travel. According to its specific applications, it is also known as wavelength-converting transponder, WDM transponder or fiber to fiber media converter. Fiber optic Transponders extend network distance by converting wavelengths (1310 to 1550), amplifying optical power and can support the “Three Rs” to Retime, Regenerate and Reshape the optical signal. In general, there is an O-E-O (optical-electrical-optical) function with this device. Fiber optic transponders and optical multiplexers are usually present in the terminal multiplexer as an important component for WDM (Wavelength Division Multiplexing) system. In addition, in nowadays market, many transponders are designed as protocol and rate-transparent fiber media converters that support SFP, SFP+ and XFP transceivers with data rates up to 11.32 Gpbs, and with seamless integration of different fiber types by converting multi-mode fiber to single-mode fiber, and dual fiber to single-fiber.

2U fiber Optic Transponder

Fiber Optic Transceiver vs Fiber Optic Transponder
A transponder and transceiver are both functionally similar devices that convert a full-duplex electrical signal in a full-duplex optical signal. The difference between the two is that fiber transceivers interface electrically with the host system using a serial interface, whereas transponders use a parallel interface. So transponders are easier to handle lower-rate parallel signals, but are bulkier and consume more power than transceivers. In addition, transceivers are limited to providing an electrical-optical function only (not differentiating between serial or parallel electrical interfaces), whereas transponders convert an optical signal at one wavelength to an optical signal at another wavelength. As such, transponders can be considered as two transceivers placed back-to-back.

Author’s Note
I hope you can start down the path to fully understanding transceivers, transponders, and the difference between them, particularly in a networking, Ethernet, or fiber-optic communications setting after reading this article. Of cause, knowledge is endless, if you still want to get more information about transceiver and transponder, I suggest that you should find more references to read. If you just need to buy the related products, I will recommend Fiberstore to you as usual.

Article Source: http://www.fiber-optic-transceiver-module.com/whats-the-difference-between-transceiver-transponder.html

SFP Transceiver Module Troubleshooting

SFP (small form-factor pluggable) is a compact, hot-pluggable transceiver module used for both telecommunication and data communications applications. With the increasing high speed data transmission demands of people, products, such as SFP+, CFP and QSFP/QSFP+ etc. have shared the market. Nonetheless, SFPs have still played an important role in telecommunication and data communication.

Transceiver-Solution

As a widely and commonly used component in data transmission, due to the incorrect operation or other factors, it is hard to avoid facing the faults in using SFP, and sometimes even result in a bad situation and heavy loss. This paper will help you to diagnose the SFP problems (take Cisco for example) and give some resolution tips. I hope it would be acted as a learning tool and a reference source for both new and experienced technicians who work in this field.

To diagnose SFP problems, you can get statistics from the browser interface, the CLI (Command Line Interface) or an SNMP (Simple Network Management Protocol) workstation. The most common SFP problems include these aspects:

  • Poor performance
  • No connectivity
  • Corrupted software

Poor Performance (or Excessive Errors)
Possible Cause:
The possible causes of this problem include that cabling distance is exceeded or port statistics show excessive frame check sequence (FCS), late-collision, or alignment errors.
Resolution:

  • Reduce the cable length to within the recommended distances.
  • See your SFP module documentation for cabling guidelines.

No connectivity
Possible Cause:
This problem is most likely related to cabling. Using incorrect or bad cable, or incorrect cable wiring, or STP (Shielded Twisted Pair) checking for possible loops may probably lead to this problem.
Resolution:

  • Verify the pinouts are correct for the proper application of cables.
  • Replace the cable with a tested good cable.
  • Wait 30 seconds for the port LED to turn green.

Corrupted software
The corrupted software here we mentioned include the following three situations.
1.The port is placed in error-disabled state after SFP is inserted.
Possible Cause:
This problem is usually caused by bad or non-Cisco-approved SFP module(ie. the incompatible SFP).
Resolution:
Remove the SFP module from the switch and replace it with a Cisco-approved module. Use the irrdisable recovery cause GBIC-invalid global configuration command to verify the port status, and enter a time interval to recover from the error-disable state. The best advice is to use the Cisco original SFP or 100% Cisco compatible SFP (If you decide to use a third-party SFP, please ensure that your supplier is assured) that is adapted to the switch.

2.Device does not recognize the SFP module.
Possible Cause:
This problem is generally related to the SFP installation. Situations, such as SFP is installed upside dowm or does not snap into the slot can cause this problem.
Resolution:

  • Verify that the SFP module is not installed upside down.
  • Remove the SFP module. Inspect for physical damage to the connector, the module, and the module slot.
  • Replace the SFP module with a known good SFP module.

3.Excessive errors found in port statistics.
Possible Cause:
Bad adapter in attached device or STP checking for possible loops can cause this problem.
Resolution:
Run adapter card diagnostic utility and wait 30 seconds for the port LED to turn green.

Some common error message of Cisco Switch When Using With SFP Module
Error Message: Transceiver module inserted in port
Explanation: The online insertion and removal (OIR) facility detected a newly inserted transceiver module for the interface specified in the error message.

Error Message: INIT_FAILURE: Detected for transceiver module in port, module disabled
Explanation: An initialization failure occurred for the transceiver module for the interface specified in the error message. This condition could be caused by software, firmware, or hardware problem. As a result of the error, the module is disabled.

Recommended Action: Try reseating the module. Hardware replacement should not occur first occurrence. Before requesting hardware replacement, review troubleshooting logs with a technical support representative.


Error Message: NOT_IDENTIFIED: Detected for transceiver module in %s, module disabled
Explanation: The transceiver module for the interface specified in the error message could not be identified and may not be compatible with the interface. The transceiver module specified in the error message contains a transceiver code which could not be correctly interpreted. As a result of the error, the module is disabled.

Recommended Action: Replace the module with a compatible transceiver.


Error Message: UNSUPPORTED-TRANCEIVER: Unsupported SFP transceiver found on board. Warranty/support may void
Explanation: The transceiver module for the interface specified in the error message is not a Cisco supported module. As a result of the error, the module is disabled. When Cisco determines that a fault or defect can be traced to the use of third-party transceivers installed by a customer or reseller, then, at Cisco’s discretion, Cisco may withhold support under warranty or a Cisco support program. In the course of providing support for a Cisco networking product Cisco might require that the end user install Cisco transceivers if Cisco determines that removing third-party parts will assist Cisco in diagnosing the cause of a support issue.
Recommended Action: None.

Related Article: How to Install SFP transceiver?

How To Choose The Right Fiber Patch Cable For Your Cisco Fiber Optic Transceivers

As we know, according to the interface of Ethernet, the common used pluggable modules include the three types. Copper cable, usually with RJ45, direct attech cable and the pluggable transceiver modules with the patch cables, as the following picture shows. Here, the copper cable, we also call copper patch cord. The direct attach cable (short for DAC) is used to connect one mobility access switch with another when forming a stack which is widely applied in storage, data, and high-performance computing connectivity. But they are both not today’s main topic.

Pluggable-Modules

With the increasing demands of higher transmission, people may be more prefered to use fiber optic cables when considering network cabling. Comparied to DAC, due to its flexibility, the use of fiber optic transceiver modules and fiber patch cable plays an important role in fiber optic data transmission, especially data transmission between the switches and equipment, and now are widely used in both telecommunication and data communications. However, when choosing fiber patch cables for our transceiver modules, it seems to be a headache for many users on how to choose a right fiber patch cable. Today, I want to take the Cisco fiber optic transceiver module as an example to discuss this topic.

Actually, before starting this topic, it is necessary for us to review the basic knowledge of the fiber optic transceiver module and fiber patch cable.

Fiber Optic Transceiver Modules
Fiber Optic Transceiver Module is a self-contained component that can both transmit and receive. Usually, it is inserted in devices such as switches, routers or network interface cards which provide one or more transceiver module slot. The fiber optic transceivers here we metioned include the SFP, SFP+ and X2 etc. Since we have discussed each of these not long ago, we may not repeat them here. Wanna review and get more details please visit the previous post.

transceiver module

Fiber Patch Cable
Fiber Patch Cable, also known as fiber jumper or fiber optic patch cable is designed to interconnect or cross connect fiber networks within structured cabling systems. According to fiber cable mode, cable structure or connector types etc., fiber patch cable can be divided into different types.

fiber patch cable

Fiber Cable Mode – there are single mode fiber patch cable and multimode fiber patch cable. The word mode means the transmitting mode of the fiber optic light in the fiber optic cable core. Single mode patch cables are with 9/125 fiber glass and are yellow jacket color, while multimode patch cables are with OM1 62.5/125 or OM2 50/125 fiber glass and are orange color. In addition, there is 10 Gigabit Laser Optimized OM3 and OM4 which cable jacket are usually aqua.

Fiber Cable Structure – simplex fiber patch cable is consist of single fiber core, while duplex fiber patch cable is consist of two fiber cores and can be either multimode or singlemode. Additionally, there is also ribbon fan-out cable assembly (ie. one end is ribbon fiber with multi fibers and one ribbon fiber connector such as MTP connector (12 fibers), the other end is multi simplex fiber cables with connectors such as ST, SC, LC, etc.).

Connector Types – Fiber optic patch cable can be also classified by the types of fiber optic connector. For example, LC fiber optic patch cable is named as it is with LC connector. Similarly, there are SC, ST, FC, MT-RJ, E2000, MU and MPO/MTP fiber optic patch cables. What’s more, there are PC, UPC, APC type fiber patch cords, which are differentiated from the polish of fiber connectors.

connector types

How To Choose The Right Fiber Patch Cable For Your Cisco Fiber Optic Transceivers
We suppose that we need to choose a right patch cable using between Cisco fiber optic transceiver SFP-10G-SR and X2-10GB-SR. How should we do? According to “Cisco 10-Gigabit Ethernet Transceiver Modules Compatibility Matrix“, we may know that SFP-10G-SR is the 10GBASE-SR SFP+ transceiver module for MMF, 850-nm wavelength, LC duplex connector. And X2-10GB-SR is the 10GBASE-SR X2 transceiver module for MMF, 850-nm wavelength, SC duplex connector. Obviously, when we require X2-10GB-SR has SC connector, and the SFP-10G-SR has LC connector. so that we would require patch cable with SC-LC connector with MMF, 850-nm wavelength. In the same way, we could choose right fiber patch cable for your other transceiver modules. Of cause, if your transceiver modules are not Cisco’s, you need to ask your brand supplier to get the corresponding compatibility matrix.

Fiberstore Fiber Optic Transceivers & Fiber Patch Cable Solutions
Fiberstore provide various types of fiber patch cords including single mode, multimode, multi core, and armored versions. You can aslo find fiber optic pigtails and other special patch cables here. For most of them, the SC, ST, FC, LC, MU, MTRJ, E2000, APC/UPC connectors are all available, even we supply MPO/MTP fiber cables.

Fiberstore provide a full range of optical transceivers, such as SFP+ (SFP Plus) transceiver, X2 transceiver, XENPAK transceiver, XFP transceiver, SFP (Mini GBIC) transceiver, GBIC transceiver, CWDM/DWDM transceiver, 40G QSFP+ & CFP, 3G-SDI video SFP, WDM Bi-Directional transceiver and PON transceiver. All our fiber transceivers are 100% compatible with major brands like Cisco, HP, Juniper, Nortel, Force10, D-link, 3Com. They are backed by a lifetime warranty, and you can buy with confidence. We also can customize optical transceivers to fit your specific requirements.

Related Article: How to Select 10G SFP+ Modules for Cisco Switches?

The Chanllenges of Technology And Cost 100G Faced

More and more high bandwidth services such as high definition(HD) video, online games and video conference challenging the traditional network, 100G as a ease network bandwidth technology, becomes the new hope of the operator.

100G industry chain has matured, with all components and subsystems have commercial capacity of multiple manufacturers, the market also needs the support of 100G system, the backbone network will be fully transferred to the 100G-leading era. From the early 2013, the focus point of 100G is from the laboratory into 100G network deployment and the commercial 100G has started.

Four Technical Challenges Of 100G

Although the 100G has been carried out, but the 100G transmission technology meets four technical challenges.

First, high power consumption. The achievement mechanism of 100G technology is complex, the optical receiver requires the use of coherent reception and processing of the DSP, the key chip has no ASIC, resulting in high power consumption of the whole 100G system. When large-scale commercial 100G technology, the average power consumption of each wavelength is still a problem waiting to be solved. Currently the power consumption of per wavelength is above 200W, the average power consumption of per frame is 7000W, so there will need three frames. Obviously, the 28nm process can help to reduce energy consumption, but there is no 100G solution of 28-nanometer. In addition, although the light energy consumption is not large, but due to the use of next-generation fiber optic transceiver will increase greatly, reducing the power consumption is very necessary.

The second is integrated, especially in the field of optical circuit and photoelectric integration. How to add mass active and passive optical devices such as laser, fiber optic amplifier, wavelength division multiplexing(WDM) and transmitter/receiver to the network to achieve highly integrated? Using semiconductor technology to the integration of CWDM and laser?

The third is test. The challenges of 100G testing include the quality evaluation of the deployed 100G system signal and the system maintenance after deployed. 100G using polarization multiplexing, and the signal spectrum is wide, the common OSDR and test instruments can not real-time test it, only by shutting off the laser method. How to achieve real-time test is industry’s future research topic, many of today’s online testing system are worth studying.

The Fourth is few prospective studies. How to make the current transmission system gradually shift to user-oriented management from the traditional network management? Quickly and efficiently allocate the physical resources?

The key is the problem of cost

The key reason why 100G failed to be applied large-scale currently is the opportunity cost is relatively too high. In the era of 100G, the cost of optical module is very high. The mainstream CFP module, the actual sales price is more than $10,000. From the point of optical module cost, 100G module is several times higher than 10G optical module. It also requires manufacturers continue to make efforts in chip integration, integrated optical module miniaturization and system design, to achieve the overall cost of products are reduced.

Especially the regard of optical module technology, the cost of this part is the key of the whole 100G system cost, the optical module itself has to face the challenges of control power consumption and improve board integration.