Category: Fiber Transceivers

Recently the building of QSFP-DD (Multi Source Agreement) Group has excited optical communication industry. This group, including 13 members which are all the leading vendors in the industry, like Cisco, Brocade and Finisar, aims to create a upgraded version of QSFP transceiver, which is called QSFP-DD ( double density QSFP) and will be able to support 200G/400G Ethernet.

Introduction

The QSFP-DD is similar to the current QSFP. But there are many differences between the current QSFP. The reason why the new transceiver is called “double density” is related to the current 100G QSFP28 transceivers. The “double density” means the doubling of the number of high-speed electrical interfaces that the module supports compare to regular QSFP28 module.

QSFP-DD and QSFP28

We can understand the QSFP-DD better by comparing it with the current 100G QSFP28 module. QSFP28 transceiver is a four-channel transceiver which is able to transmit and receive 100G per second simultaneously. With the advantages of high speed and low power, QSFP28 transceiver is becoming more popular than other 100G transceivers like CFP2 and CFP4. The 100G QSFP28 transceiver is implemented with four lanes with each supporting data rate of 25G.

The working principle of QSFP-DD is similar with 100G QSFP28 transceiver. The QSFP-DD MSA group will increase the lane to eight. There will be a row of contacts providing for an eight lane electrical interface in QSFP-DD. If modulated by NEZ, each lane of the QSFP-DD can support data rate up to 25G, thus, it can support a total data rate of 200G. If modulated by PAM4, it can support data rate up to 400G with each lane supporting data rate of 50G. The MSA group also announced that the QSFP-DD can enable up to 14.4Tbps aggregate bandwidth in a single switch slot, which can definitely satisfy the increasing need for higher bandwidth.

Another great feature of QSFP-DD is that its system will be backwards compatible, allowing them to support existing QSFP modules and provide flexibility for end users and system designer. This means the data center could save a considerable sum of money in the future upgrading.

Future and Present

The appearance of QSFP28 transceiver has changed the regular development road map of Ethernet. The regular upgrade road is 10G to 40G and then 100G. While the QSFP28 transceiver has changed it from 25G directly to 100G. The road map of this QSFP-DD is also drawing our attention. It is predicted that it will become a useful family of modules for the industry with application at greater than 400G. Meanwhile, there is no efforts underway to define these new speeds but it is expected that QSFP-DD will have a roadmap that supports.

Any way, no matter where the QSFP-DD lead our Ethernet to, it is good news for our future networking system. The creating of this new module will still need some time. For now, many data centers are considering about upgrading their data center with 100G QSFP28 transceivers. And there are a variety of switches which support QSFP28 interfaces on the market. However, 100G QSFP28 transceiver is still not cheap in the current market. For example, the price of a 100GBASE-SR4 QSFP28 transceiver is generally more than $2000.00. However, in fiber-mart.COM, supported by OEM, the price is much more favorable. A 100GBASE-SR4 QSFP28 transceiver only cost $650.00 in fiber-mart.COM. The following chart is detailed information of 100G QSFP28 transceivers in fiber-mart.COM.

With the development of wavelength-division multiplexing (WDM) technology, the network traffic volume is increasing and the demand for more network bandwidth is also on the rise. By converting the operating wavelength of the incoming bitstream to an ITU-compliant wavelength, WDM transponder serves as a key component in WDM system. As an important technology in the fiber optical network, WDM is moving beyond transport to become the basis of all-optical networking. And how to optimize WDM network has always been a hot topic. The transponder is a device to optimize the performance of WDM network, which plays an important in the whole system of WDM network. This article will introduce you the information on WDM transponders.

What Is WDM Transponder?

Also called as an OEO (optical-electrical-optical) transponder, a WDM optical transponder unit is an optical-electrical-optical wavelength converter, which has been widely adopted in a variety of networks and applications. The picture below shows us how a bidirectional transponder works. In this picture, the transponder is located between a client device and a DWDM system. And we can see clearly that, from left to right, the transponder receives an optical bitstream operating at one particular wavelength (1310 nm), and then converts the operating wavelength of the incoming bitstream to an ITU-compliant wavelength and transmits its output into a DWDM system. On the receive side (right to left), the process is reversed. The transponder receives an ITU-compliant bit stream and converts the signals back to the wavelength used by the client device.

The Application of a WDM Transponder

According to its function, the application of a WDM transponders can be classified into the following types.

Wavelength Conversion. It is known to us that when a CWDM Mux/Demux or DWDM Mux/Demux is added into a WDM network, there is a requirement to convert optical wavelengths like 850nm, 1310nm and 1550nm to CWDM or DWDM wavelengths. Then the OEO transponder comes to assist. The OEO transponder receives, amplifies and re-transmits the signal on a different wavelength without changing the signal content.

Fiber Mode Conversion. Multimode fiber optic cables (MMF) are often used in short distance transmission, while single-mode fiber optic cables (SMF) are applied in long optical transmission. Therefore, in some network deployment, considering the transmission distances, MMF to SMF or SMF to MMF conversions are needed. WDM transponders can convert both multimode fiber to single-mode fiber and dual fiber to single fiber.

Signal Repeating. In long haul fiber optic transmission, WDM transponder also can work as repeaters to extend network distance by converting wavelengths (1310nm to 1550nm) and amplifying optical power. The OEO converters convert the weak optical signals from the fiber into electrical signals, and regenerate or amplify, then recover them into strong optical signals for continuous transmission.

WDM Transponder and FMT Solution

At fiber-mart, OEO transponders are made into small plug-in cards to be used on the FMT platform. FMT platform makes devices like EDFA, OEO, DCM, OLP and VOA into plug-in cards and provides standard rack units as well as free software to achieve better management and monitoring. In addition, FMT series products like OEO, DCM and OLP also have higher performance than that of old ones. FMT series OEO transponder can convert optical signals into DWDM wavelengths, reducing the fault risk caused by high power consumption of DWDM fiber optic transceiver. Since the OEO transponder is made into small plug-in card in the FMT platform, it only occupies one slot in the special designed chassis when installed, thus saving a lot of space. In addition, all these FMT plug-in cards, including OEO, in a rack unit share the same power source and support hot plug & play operation. And they can be inserted or removed flexibly in the racks for DWDM networking.

Conclusion

Since the OEO or WDM transponder plays an important role in WDM network, such as receiving, amplifying and re-transmitting the signal on a different wavelength, adding an OEO transponder into the WDM network is very essential. The OEO transponders in our FMT series are made into small plug-in cards with high quality to ensure good transmission performance. For more information on our FMT system, please visit http://www.fiber-mart.com.

With the improvement of people’s living standard, nowadays a single network access gradually cannot satisfy people’s demand for network now, CWDM system support for the characteristics of business more and more get the attention of people, can also provide E, FE, GE, STM 1/4/16 SDH and ATM signaling, CATV video interface and other businesses such as access CWDM system solutions, to meet the requirements of people now.

Radio and television networks in recent business growth is faster in a given area, is the region development education network access project, due to the previous optical fiber network resources is mainly used in cable television network, optical fiber resources is not so rich, many county to the town had no residual fiber resources, to increase the data business, now want to be in the original on the fiber optic cable TV network transmission using again, plus information data signals, or want to lay out the other cable the main work, need to solve as many towns in this area belongs to mountainous area, cable laying is not very convenient, considering various factors such as resources, cost, on the radio and television networks company specialized in CWDM system to conduct a comprehensive performance analysis and product testing.And start in areas such as education network access to a project on each node USES many fiber-mart.com CWDM system equipment.

The radio and television networks of CWDM project at present is mainly used to implement the education network (10/100 MBPS Ethernet) hybrid transmission signals and the cable television network, the current direction of projects with a total of eight different contact, sharing the 3 sets of fiber-mart.com the CWDM system equipment.

In this scenario, A computer room – B node transfer 2 10/100 MBPS data signals and A cable TV signal, which is based on WDM CWDM access, two 10/100 MBPS signals after fiber-mart.com C5002S through fiber-mart.com HA – WDM multiplexer, and cable television signals and reuse all the way to A single fiber, transfer to the access point B region, middle transmission distance of 50 km, implements and Ethernet cable TV signal on the single fiber CWDM module of hybrid transmission.

A room – C nodes use sea pegatron C5002S system combined with high speed and CWDM terminal transceiver effectively cooperate with access, realize two-way 10/100 MBPS of hybrid transmission over A single optical fiber.

A-D-E by fiber-mart.com C5004S system combining various nodes of high speed and the corresponding CWDM transceiver implementation 4 10/100 MBPS signals on A single optical fiber access project, through the high speed connection between each contact, through the terminal CWDM wavelengths optical transceiver connected to A contact switch, after the C5004S system in the computer room 4 different signals, respectively in different wavelengths transmitted to each destination, after D primary school, through high speed download local signal, the remaining 3 to continue down the road signal to the corresponding destination.

Save fiber resources CWDM (Coarse where division multiplexing) Coarse wavelength division multiplexing system, which USES optical multiplexer in the different optical fiber transmission wavelength multiplexing in a single fiber transmission;On the receiving end of A link, using wavelength multiplexer and then revert to the original wavelength, using optical fiber all the way, on the whole link is solved effectively under the condition of the optical fiber resources extremely nervous network access, this scenario, A, D, E, between transmission on A single fiber and four 10/100 MBPS (also can be 1000 MBPS) signal, A room – B node is in the original cable TV signal transmission on A single fiber loading 2 10/100 MBPS signals, save A lot of fiber resources. 2.More business and high bandwidth CWDM is a according to the practical application to the transfer rate of adaptation based transmission platform, support a variety of business transfer.At each wavelength, the support of the business including 10 m / 100 m / 1000 m Ethernet, 155 m / 622 m / 2.5 G of SDH, 155 m / 622 m ATM business, as well as the Fiber Channel business, and so on.The whole system capacity to play a few Gbps data signal.Fully meet user bandwidth requirements in quite some time.This scenario USES is 10/100 MBPS business with cable TV signal for hybrid transmission.

CWDM system than the price of L band DWDM transceiver is relatively low, due to the power of CWDM is small, small volume, easy to use, thus supporting facilities, personnel training and the late maintenance cost is low.Compared with optical cable project: using CWDM device is opened rapidly, low cost, convenient network upgrades, late and increasing need of signal directly, or replace the higher rate of product, don’t need to change the fiber link, convenient network upgrades, reduces the network upgrade costs.The above scenario A-D-E, if change into 1000 MBPS data signals, the capacity of the network directly to upgrade to the 4 GBPS.

CWDM in hybrid access network in the use of the business.

Recently the building of QSFP-DD (Multi Source Agreement) Group has excited optical communication industry. This group, including 13 members which are all the leading vendors in the industry, like Cisco, Brocade and Finisar, aims to create a upgraded version of QSFP transceiver, which is called QSFP-DD ( double density QSFP) and will be able to support 200G/400G Ethernet.

Introduction

The QSFP-DD is similar to the current QSFP. But there are many differences between the current QSFP. The reason why the new transceiver is called “double density” is related to the current 100G QSFP28 transceivers. The “double density” means the doubling of the number of high-speed electrical interfaces that the module supports compare to regular QSFP28 module.

QSFP-DD and QSFP28

We can understand the QSFP-DD better by comparing it with the current 100G QSFP28 module. QSFP28 transceiver is a four-channel transceiver which is able to transmit and receive 100G per second simultaneously. With the advantages of high speed and low power, QSFP28 transceiver is becoming more popular than other 100G transceivers like CFP2 and CFP4. The 100G QSFP28 transceiver is implemented with four lanes with each supporting data rate of 25G.

The working principle of QSFP-DD is similar with 100G QSFP28 transceiver. The QSFP-DD MSA group will increase the lane to eight. There will be a row of contacts providing for an eight lane electrical interface in QSFP-DD. If modulated by NEZ, each lane of the QSFP-DD can support data rate up to 25G, thus, it can support a total data rate of 200G. If modulated by PAM4, it can support data rate up to 400G with each lane supporting data rate of 50G. The MSA group also announced that the QSFP-DD can enable up to 14.4Tbps aggregate bandwidth in a single switch slot, which can definitely satisfy the increasing need for higher bandwidth.

Another great feature of QSFP-DD is that its system will be backwards compatible, allowing them to support existing QSFP modules and provide flexibility for end users and system designer. This means the data center could save a considerable sum of money in the future upgrading.

Future and Present

The appearance of QSFP28 transceiver has changed the regular development road map of Ethernet. The regular upgrade road is 10G to 40G and then 100G. While the QSFP28 transceiver has changed it from 25G directly to 100G. The road map of this QSFP-DD is also drawing our attention. It is predicted that it will become a useful family of modules for the industry with application at greater than 400G. Meanwhile, there is no efforts underway to define these new speeds but it is expected that QSFP-DD will have a roadmap that supports.

Any way, no matter where the QSFP-DD lead our Ethernet to, it is good news for our future networking system. The creating of this new module will still need some time. For now, many data centers are considering about upgrading their data center with 100G QSFP28 transceivers. And there are a variety of switches which support QSFP28 interfaces on the market. However, 100G QSFP28 transceiver is still not cheap in the current market. For example, the price of a 100GBASE-SR4 QSFP28 transceiver is generally more than $2000.00. However, in fiber-mart.COM, supported by OEM, the price is much more favorable. A 100GBASE-SR4 QSFP28 transceiver only cost $650.00 in fiber-mart.COM. The following chart is detailed information of 100G QSFP28 transceivers in fiber-mart.COM.

Optical fibers require end-surface treatment for proper light propagation and that includes polishing their ends. Polishing is essential for almost all glass-based fibers with cladding diameters larger than 200 microns. Furthermore, all fiber connectors require polishing. The process of fiber optic polishing can occur in the field or in a technical lab, it employs a range of tools and products used to create precision fits and finishes in the delicate glass ends.

There is typical fiber optic polisher for fiber optic polishing. Fiber Optic Polishing Machines are used to polish the end faces of fiber optic products (cables, connectors, adapters, etc.) in order to minimize signal losses due to scattering. Polishing machines can increase productivity by providing rapid polishing of many different connector styles.

When selecting a fiber polishing machine, there are several features to consider, including adjustable pressure, changeable holders, a timer, and the ability to request custom specifications. Most polishing machines do not offer the flexibility of speed adjustment. This is partially due to the fact that most users only need to handle one type of ferrule material such as zirconia. A slight speed variation does not have significant impact on connector polish result. However, a versatile polisher should have the capability to change speed according the ferrule and polishing film material.

The polishing job typically involves fusion splicer, among other network crimping tool and connectors are needed. It also requires 99% isopropyl alcohol, polishing (lapping) film and pad, a polishing puck, and epoxy or adhesive. Some technicians also find needle, syringe, and piano wire useful.

Several Different Polish Options On Fiber Connectors

The different polish of the fiber optic connector ferrules result in different performance of them, mainly on the back reflection (return loss). Generally, PC type is required at least 40dB return loss or higher, UPC is 50dB or higher, APC is 60dB or higher. (As we know, the higher the return loss, the better the performance). Insertion loss of them all should be less than at least 0.3dB, the lower the insertion loss the better the performance.

Things You Need To Mind During Fiber Optic Polishing

It is important not to dwell on any polishing film longer than necessary. Too much polishing can result in undesirable ferrule length, unnecessary polish film wear, and degraded polish finish due to particle accumulation. Make proper adjustments to the recommended polishing time in each step in case they are less than ideal.

Eye protection is always necessary to protect against powerful industrial lasers used in long-distance single-mode networks. Supporting tools may include a visual fault locater to troubleshoot fiber faults and breaks. A fiber-optic inspection microscope permits precision analysis of hair-fine fibers. Additionally, technicians rely upon jacket strippers, cutters, cable slitters, and fusion splicers.

Conclusion

Fiber polishing is a science but much like an art. The science of polishing is crystallized in a well designed machine while the art of polishing reside in the procedure and the continuous effort for improvement by the individual user. The procedure and the training are just as valuable as the polishing machine.

In previous articles, we have mentioned of the connector cleaning. And we know any contamination in the fiber connection can cause failure of the component or failure of the whole system. Fiber optic connector is an important component in fiber connection. And today, I want to introduce the fiber optic polishing in this article. As we know, fiber optic cables require end-surface treatment for proper light transmission. Polishing is an essential step for almost all glass-based fibers with cladding and diameters larger than 200 microns and all fiber optic connectors also need polishing. So, why do we need fiber optic connector polishing and what types are there of fiber optic connector polishing? We will describe in the following.

Why We Need Fiber Optic Connector Polishing?

It is known that, once the fiber optic cable is terminated with a particular connector, the connector end-face preparation will determine what the connector return loss(we generally call back reflection) will be. The back reflection is the ratio between the light propagation through the connector in the forward direction and the light reflected back into the light source by the connector surface.

It is very important to minimize the back reflection in high-speed and analog fiber optic links, utilizing narrow linewidth sources such as DFB lasers, which are prone to mode hopping and fluctuations in their output. Polishing is one of the essential procedure to make fiber optic connector work perfect. That’s why we need fiber optic connector polishing.

Fiber Connector Polishing Ways

There are several different polish options on the fiber connectors. Due to the extreme accuracy requirement of today’s fiber connections, polishing is mostly done by a machine, especially for the production. But there are also some of non-production types of terminations still done by hand.

The common machine polishing tools, such as fiber optic polishing machines and other fiber optic polishing machine kits including fiber polishing fixture for all types of fiber optic connectors. while the manual fiber optic connector polishing will need polishing paper and  fiber optic polishing puck or some cleanser. Some of the fiber optic polishing tools look as the following picture.

1. Flat Polished(Flat)

A flat polished connector has zero dome-shaped geometry.

flat-polish

2. Physical Contact(PC)

PC connector is polished in a dome-shaped geometry to maximize the signal transmitted at the connection.

Physical contact

3. Ultra Physical Contact (UPC)

The ultra physical contact describes connectors that undergo extended polishing to render the fiber end-face more suitable for optical contact with another fiber than an ordinary PC connector.

ultra physical contact

4. Angled Physical Contact (APC)

Angled physical contact connector is polished on an 8° angle. When compared with a normal “physical contact” (PC) connector, an APC connector exhibits better reflected properties, because the angled polish reduces the amount of light reflected at the connector interface. Connector types available with an angled polish include SC, ST, FC, LC, MU, MT, and MTP.

angled physical contact

Conclusion

Fiber polishing is as much a science as it is an art. To a certain extent, proper polishing of fiber optic polishing is critical for optimum results. However, it also depends on your polishing machine or your own technique. So do not just working like horse, select the right machine or the right company for your fiber optic connector and polishing tool.