Why You Should Choose 100G QSFP28 Optical Transceivers

The continuous and rapid development of the Internet as well as the desire of people for higher speed optical networks facilitated the vigorous development of the entire optical communications industry and strongly promoted the independent R & D and innovation in many core technologies including optoelectronic devices technologies. 100g optical transceiver is regarded as the product of this big data era.

The first generation of 100G optical modules is CFP optical module with very large volume, then CFP2 and CFP4 optical modules appears. CFP4 optical module is the latest generation of 100G optical module, the width is only 1/4 of CFP optical module. Its package size is not same as the QSFP + optical module. The QSFP28 optical module has a smaller package size than the CFP4 optical module, which means the QSFP28 optical module has a higher port density on the switch. The following are several 100G QSFP28 series optical modules:

Main Types of QSFP28 Optical Transceivers

100G QSFP28 LR4 is a 100Gb/s transceiver module designed for optical communication applications compliant to 100GBASE-LR4 of the IEEE P802.3ba standard.

100G QSFP28 SR4 is a four-channel, pluggable, parallel, fiber-optic QSFP+ SR4 optical transceiver module for 100/40 Gigabit Ethernet, Infiniband DDR/EDR and 32GFC applications.

100G QSFP28 PSM4 is a four-channel, pluggable, parallel, fiber-optic QSFP28 PSM4 optical transceiver module for 100/40 Gigabit Ethernet and Infiniband DDR/EDR Applications.

100G QSFP28 CWDM4 is a 100Gb/s transceiver module which is designed for optical communication applications compliant with the QSFP MSA, CWDM4 MSA and portions of IEEE P802.3bm standard.

Of course, QSFP28 series also includes 100G QSFP28 active optical cables; these products have played an important role in the development of 100G.

Advantages of 100G QSFP28 Optical Transceivers

1. Power Consumption

The power consumption of QSFP28 typically is no more than 3.5W, while the power consumption of other 100G optical modules typically is between 6W and 24W. From this, the power consumption of QSFP28 optical modules is much lower power than other 100G optical modules.

2. Cost

Now the data center is mainly 10G network architecture, in which the interconnection solutions are mainly 10GBASE-SR optical module and duplex LC multimode fiber jumper. If the existing 10G network architecture based on the direct is upgraded to 40 / 100G network, it will save a lot of time and cost. Therefore, one of the major interconnection trends in data centers is to upgrade from 10G networks to 40 / 100G networks without changing existing duplex multimode infrastructure. In this case, the MPO / MTP branchable cable is undoubtedly the ideal solution for a 10G upgrade to 40 / 100G.

3. Bandwidth

The QSFP28 uses the advanced 100G transport technology to provide the data center with a connection between the chassis switch and the core network, providing up to 150% greater panel bandwidth density than the 40G QSFP solution

Optical Module Test

When using optical modules, test performance is an essential step. Optical module is composed of transmitter and receiver, so when we test, it is generally divided into four steps, which mainly includes the transmitter and receiver test.

First, the transmitter part:

When testing, pay attention to the wavelength and shape of the transmitter output waveform, as well as the receiver’s jitter tolerance and bandwidth. When testing the transmitter, note the following:

1. The quality of the input signal used to test the transmitter must be good enough. In addition, the quality of the electrical measurements must also be confirmed by jitter and eye measurements. Eye diagram measurements are a common way to check the transmitter’s output waveform because the eye diagram contains a wealth of information that reflects the overall performance of the transmitter.

2.The output optical signal of the transmitter must be measured by the optical quality index such as eye pattern test, optical modulation amplitude and extinction ratio.

Second, the receiver part:

Unlike test transmitters, the quality of the optical signal must be sufficiently poor when testing the receiver that a light pressure eye pattern representing the worst signal must be created. This worst case optical signal must pass through jitter measurements and light Power test to calibrate.

1. Eye pattern test, this will ensure that the eye “eye” is open. Eye diagram testing is usually done at the depth of the bit error rate;

2. Jitter test to test different types of jitter;

3. Jitter Tracking and Tolerance, testing the internal clock recovery circuit to track the jitter.

All in all, testing light modules is a complex undertaking, but it is also an indispensable step in ensuring good performance. Eye diagram measurement is a widely used measurement method that can effectively test the transmitter of an optical module. The optical module receiver test is more complex, but also requires more testing methods.

A Detailed Introduction on CWDM Optical Modules

CWDM optical module adopts CWDM technology, which can combine optical signals with different wavelengths through an external wavelength division multiplexer. It saves fiber resources by transmitting through one optical fiber. At the same time, the receiving end needs to use the wave-demultiplexer to decompose the complex optical signal. In addition, CWDM optical modules can be plugged into switch or router SFP ports. This article will describe in detail what CWDM optical modules are and what are the differences between CWDM optical modules and other modules.

The Main Form Factors and Type of CWDM Optical Modules

There are three types of CWDM optical module form factors: SFP, SFP + and XFP. The transmission distance is generally as follows: 40KM, 80KM, 100KM, and 120KM.

CWDM optical modules can be divided into: CWDM SFP optical module, CWDM GBIC optical module, CWDM SFP + optical module, CWDM XFP optical module, CWDM X2 optical module, CWDMXENPAK optical module and CWDM LX-4 optical module.

The Differences between CWDM Optical Modules and Ordinary Optical Modules

CWDM optical modules are passive modules that do not emit laser. They generally use optical planar waveguide (PLC) technology; just a beam of light is divided into several beams of light. The ordinary optical modules belong to the photoelectric conversion device, which are active optical modules. Each module has two ports for receiving and transmitting, and the launch port inside is a laser.

CWDM Optical Modules VS DWDM Optical Modules: Which One to Choose?

The principle of DWDM optical modules is similar to CWDM optical modules, except that DWDM optical module are optical modules for dense wavelength division multiplexing, and has 40 common channels to choose from.

CWDM optical modules are widely used in schools, data centers, FTTH (Fiber to the Home), 1G and 2G Fiber Channel, metro Ethernet, security and protection systems and other fields.

DWDM optical modules are mainly used in long-distance optical synchronous digital transmission networks, such as Ethernet / Fiber Channel with 200km links and 80km links.

From a cost point of view, CWDM optical modules are cheaper than DWDM optical modules. CWDM optical modules provide a convenient and cost-effective solution for using Gigabit Ethernet and Fiber Channel.

DWDM optical modules, on the other hand, typically use denser channel spacing and are used for large optical networks over longer distances. If you want long-distance SFP modules, DWDM optical modules are the ideal choice.

The Differences between CWDM4 and PSM4 

CWDM4 optical module transmission rate is 103.1Gbp, mainly used in computing, high frequency trading and other fields. Its cost is significantly higher than QSFP28 PSM4.

1. The optical transmitter: PSM4 needs four integrated silicon photonic modulator and a distributed feedback laser, and CWDM4 needs four CWDM direct modulation laser;

2. The connector: PSM4 needs a MPO connector with 8 fibers, CWDM4 needs duplex LC connector;

3. The optical fiber: PSM4 is a ribbon SMF (8 core), CWDM4 is a duplex SMF;

4. The transmission distance: PSM4 is 500 meters, CWDM4 is 2000 meters

5. The four wavelength of CWDM multiplexer: PSM4 does not need, but CWDM4 needs.

In Conclusion

CWDM optical modules are multi-rate optical modules with 20-40km, 40-80km and 80-120km transmission distances. The optical modules of different wavelengths are marked with different colors to better meet customer requirements.

What Are the Impacts of High or Low Temperature on Optical Transceivers?

The working temperature of optical transceivers affects all the parameters of optical transceivers. If the ambient temperature of the optical transceiver changes, the operating current of the optical transceiver will vary with temperature. At the same time, the parameters of the optical transceivers change, which affects the normal transmission of optical transceivers. Today, we mainly talk about the causes of too high or too low temperature on optical transceivers and its impact.

What Is the Normal Temperature of Optical transceivers?

Because the type and brand of the optical transceiver are complicated, the temperature of modules corresponding to different optical transceiver temperature levels are different and the temperature specifications defined by the supplier are different, whether the temperature of optical transceivers is abnormal or not needs to be considered according to these factors. Before we use the optical transceiver, it is best to check the vendor’s definition of the temperature profile of the optical transceiver so as to reduce the number of problems caused by abnormal optical transceiver temperature.

Optical transceiver temperature mainly includes three levels: commercial grade, extended grade, industrial grade. The following is a detailed description of these three temperatures:

Temperature Grade Abbreviation

 

Temperature Range
Commercial temperature range COM 0 ~ + 70 ℃
Extended temperature range EXT -20 ~ 85 ℃

 

Industrial temperature range IND -40 ~ 85 ℃

 

Three Reasons That Affect the Temperature of Optical Transceivers

1. The Poor Quality and Workmanship

If you use the optical transceivers with poor quality and workmanship, then the phenomenon of abnormal temperature of the optical transceivers is more common. Because the function of such optical transceivers is instable, heat dissipation is also relatively poor. In order to reduce the temperature anomaly and unnecessary discard, we advise to use the optical transceivers with better function, quality and workmanship.

2. The Harsh Application Environment

Optical transceiver operating environment is in the data center, computer room or interchanger. If the optical transceivers are used in other environments, the change of the ambient temperature will inevitably change the temperature of the optical transceiver, thereby affecting its optical power and optical sensitivity. If the application environment of optical transceivers is harsh, then we advise to select the optical transceivers with industrial temperature or extended temperature.

3. The Use of Second-hand Optical Transceivers

The temperature of new optical transceivers is usually at 0-70 ° C and many second-hand optical transceivers are inaccessible. And the second-hand optical transceivers cannot operate normally in high-temperature or low-temperature conditions. Therefore, we advocate the use of new optical transceivers.

What Are the Impacts of High or Low Temperature on Optical transceivers?

If the optical transceiver temperature is too high or too low, it will affect the function of the optical transceiver and make the communication data appear faulty. The optical transceivers will alarm if its temperature isn’t in the normal range. If the optical transceivers are in a bad situation, interchangers will send data continuously. The optical transceivers will not send / receive data from the beginning until it is recovered to normal operation.

1. The Impact of Too High Temperature on Optical Transceivers:

If the operating temperature of optical transceivers is too high, the optical power of optical transceivers will become larger and the receiving signal will be faulty, and even the optical transceiver will be burned. As a result, the optical transceivers cannot work normally. In this case, DDM function should be added. You can select temperature control system for real-time monitoring and compensation to ensure that the optical transceiver extinction ratio and luminous power stable, to ensure the normal operation of the optical communication system.

2. The Impact of Too Low Temperature on Optical Transceivers:

Generally speaking, as long as optical transceivers are not exposed to the harsh environment below 0℃, the temperature will not be too low. It is better not to use the optical transceiver in the condition of too low temperature, as this may cause the function of the optical transceiver to be unstable.

How about the Temperature of Gigalight’s Optical Transceivers?

As one of the most top-rated optical transceiver vendors in China, Gigalight complies with the temperature grade standard that the industry requires, and will meet the customer demand for temperature. In addition, all optical transceivers will undergo a high and low temperature burn-in test prior to shipping to test the temperature to ensure the quality of the products.

 

Something about 100G Optical Transceivers That You Want to Know

With the development of science and technology, the application of optical communications products in real life is becoming more and more widespread. The demand for network technology is also getting higher and higher. Therefore, 100G optical transceivers are gradually appearing on the market. The development of 5G and Data Center further make the 100G optical transceivers become the mainstream of the optical transceiver market gradually. Perhaps you have had a certain understanding of 100G optical transceivers, but if we analysis 100G optical transceivers from another point of view, you will find something different.

Development Background of 100G Optical Transceivers

For the earliest developed 100G optical transceiver, the form factor is CFP, developed in 2010. At that time, IEEE launched 100G optical transceiver SR10, LR4 and ER4 three standards, separately aiming at the 100m, 10Km and 40Km transmission. Followed by that, the IEEE standard added the new 100G SR4 project, but in 2013 did not reach consensus and vacancies. By 2016, the 100G optical transceivers used by various data centers were mostly the 25Gbps Serdes program, and the 100G optical transceivers that use the 50Gbps Serdes planned slowly appeared.

The Facing Problems for 100G Optical Transceivers

1. Channel Distance: The DWDM system supporting the 50GHz wavelength distance is very extensive. The 100G optical transceiver needs to meet the condition of supporting the 50GHz wavelength distance, therefore, the pattern of high spectral power should be used.

2. OSNR (optical signal-to-noise ratio): Under the same pattern, 100G optical transceivers requires10dB higher than 10G optical transceivers and 4dB higher than 40G optical transceivers. Therefore, a low OSNR tolerance code and high coding gain FEC algorithm are needed.

3. CD Margin: Under the same conditions, 100G optical transceiver dispersion tolerance only needs 1/100 of 10G optical transceiver, accounting for 16/100 of 40G optical transceiver. Therefore, 100G optical transceivers can use dispersion compensation technology, in the electric field or the optical domain compensation to complete the dispersion compensation for each wavelength.

4. PMD Tolerance: Under the same conditions, PMD (polarization mode dispersion) tolerance of 100G optical transceiver is 1/10 of 10G optical transceivers, accounting for 4/10 of 40G optical transceiver, so you need to choose coherent reception plus digital signal processing.

5. Nonlinear Effects: Compared with 10G / 40G optical transceiver, the nonlinear effects of 100G optical transceivers are messier.

The Types and Advantages of 100G Optical Transceivers

The main form factors of 100G optical transceiver include: CFP, CFP2, CFP4 and QSFP28. To compare their advantages, the main factor to consider is the costs and power consumption for Data Centers.

1. CFP optical transceiver supports all C-band wavelengths tunable and can complete the link detection, which use a common optical dual-binary modulation format ODB, convenient layout, power consumption is less than 24W.

2. The volume of CFP2 optical transceiver is one-half of CFP, its integration is 2 times CFP. It can complete the wide dynamic input range based on SOA to achieve stable admission sensitivity, support a full CFP optical transceiver, its low power consumption is lower than 9W.

3. The volume of CFP4 optical transceiver is one-half of CFP2, its integration is twice that of CFP2, front panel port density is also doubled compared with CFP2. CFP4 optical transceiver follows the MSA protocol, support the same rate as CFP/CFP2. Its transmission power increases significantly, but the power consumption drops significantly, only about half of the original, the system cost is lower than the CFP2. In addition, CFP4 optical transceiver uses 4 * 25 forms, through the 4 * 25G channel, complete 100G transmission. The transmission power is higher with higher stability.

4. The form factor of QSFP28 optical transceiver is smaller than the CFP4 optical transceiver. QSFP28 optical transceiver power consumption is generally not more than 3.5W, the use of QSFP28 optical transceiver can directly upgrade from 25G to 100G not through 40G, and therefore the cost is lower.

 

Types Standard The Largest Transmission Distance Connector Channel Wavelength Fiber Types
CXP SR10 100m MPO24 12*10G 850nm MMF
CFP/CFP2/CFP4

(CFP4 doesn’t support SR10)

SR10 100m MPO24 10*10G 850nm MMF
LR4 10km Dual LC 4*25G 1310nm SMF
ER4 40km Dual LC 4*25G 1310nm SMF
ZR4 80km Dual LC 4*25G 1310nm SMF
QSFP28 SR4 100m MPO12 4*25G 850nm SMF
LR4 10km LC 4*28G 1310nm SMF
ER4 40km LC 4*25G 1310nm SMF
ZR4 80km LC 4*25G 1310nm SMF
CWDM4 2km Dual LC 4*25G 1310nm SMF
PSM4 2km MPO 4*25G 1310nm SMF

 

Conclusion

Learning the contents of the 100G light module, above, do you have any further information? From the development trend, QSFP28 optical transceiver and CFP series optical transceiver are 100G network hot solutions, and the use of CXP will be less and less. Gigalight, as a veteran optical transceiver manufacturer with professional technology, advanced R & D capability and stable manufacturing capability, not only has many popular 100G optical transceiver products, like 100G QSFP28 CWDM4, 100G QSFP28 PSM4, CFP2 100G LR4, and etc. but also will release more new 100G optical transceivers in the first quarter of this year. More information about 100G optical transceivers, please visit the official website.

 

5G Network Drives the Development of Optical Module Market

Mobile communication is an important driving force for the development of optical networks. It is also self-evident that the development of optical modules is of great importance. We know that the optical module market can be subdivided into the Telecom market, the Datacom market and the Access market. Among them, the Telecom market is the “main battlefield” competed by the optical module industry. The biggest surprise for the future Telecom market is the evolution of 5G technology. Based on the requirement of 5G higher rate, higher capacity and higher base station density, there will be greater new demand and market space for high rate optical modules.

The Demands of Optical Transceivers for 5G Network

Although the current 5G is still in the standard stage, major equipment manufacturers have actively carried out joint trials with operators to strive to achieve 5G commercial use by 2020. “5G is commercial, carrying is the first.” It is predicted that the future number of 5G base stations will exceed 10 million, which will bring the surge in demand for optical modules in quantity. Compared with 4G technology, 5G data transmission rate is 10 to 100 times that of 4G, which means that the number of optical modules used by a single base station will increase substantially when the optical module rate remains unchanged.

We simply use a formula to represent the demand of a 5G optical module: optical module requirement (F) = base station number (m) * single base station module requirement (n). In the 5G era, compared with 4G, m and n will be significantly improved. Therefore, under the 5G construction period, the optical module will become one of the most flexible segments in the 5G industry chain. In addition, the demand for optical modules for the construction of large-scale data centers will also increase with the outbreak of 5G traffic.

To sum up, it is helpful for optical module suppliers to get ahead in the 5G era when they grasp the demand for optical modules in 5G networks in advance. So what are the specific demands of 5G optical modules? What are the mature products in the industry can initially meet the needs of 5G load? We try to analyze in the following parts.

Why Will the 100G Optical Transceivers Become the Mainstream for 5G Network?

Compared with 4G networks, 5G rebuilds the BBU into a separate architecture of CU (Centralized Unit) and DU (Distributed Unit), so its bearer needs an additional layer of intermediate network. Fronthaul – middlehaul – backhaul, the three carrier network requirements for optical modules are different. For 5G fronthaul, the CPRI bandwidth per 10MHz single-antenna port is about 614.4Mbps under ideal transmission conditions. The typical 5G wireless bandwidth is 100M ~ 1G, the peak is 20G, the antenna port may be 64 or 128. After a simple conversion, 5G fronthaul network granularity should be 25Gbps, which has been generally accepted by the industry. It can be inferred that the future 50Gbps and 100Gbps of the 5G pre-transmission modules will be the mainstream. For 5G middlehaul, it will use DWDM ring network structure, transmission distance 10 ~ 40km, n * 25G technology. This means that 100G optical modules are highly likely candidates for 5G messenger. For 5G backhaul, either with the network can be merged, but also separate. According to the future OTN networking, n * 100G technology will be adopted; if there is no OTN networking and 200G / 400G optical module technology. But no matter what kind of technology, 100G and above ultra-high-speed optical module must become the mainstream for the 5G market.

Conclusion

In conclusion, the demand of the 100G optical module by the 5G network is very urgent. At present, there are many kinds of mature 100G optical transceivers in the market, like 100G QSFP28 CWDM4, 100G QSFP28 PSM4 and 100G CFP / CFP2 / CFP4 optical modules provided by Gigalight. They cover the mainstream form factors: CFP / CFP2 / CFP4 / QSFP28 and can be used for a variety of optical network bearer demand. In particular, 100G QSFP28 and 100G CFP4 have the advantages of more compact, high module integration, transmission efficiency, power consumption and cost-effectiveness.

Introduction on the 100G CFP MSA

100G optical module is an important part of the high-speed optical transmission network. Some people say that the optical module has the status of a vice commander in the entire communication system. The rapid development of optical fiber network, people in the communication industry are obvious to al. 100G optical module is regarded as the mainstay of the 5G network, the market has to tell all of us with the truth that the optical module has changed the original market structure.

 

Speaking of 100G optical module standards and types, the market mainstream models are mainly CFP / CFP2 / CFP4 and QSFP28. As an early appeared optical module, CFP is now gradually replaced by QSFP28. But the basic principle of the optical module has not changed, and we still can learn it to understand the 100G optical module. Today we will talk about what CFP is and the 100G CFP multi-source agreement (MSA).

What Is CFP Optical Transceiver?

Designed primarily for the 100G market, the CFP optical transceiver is specifically sized for long range interfaces and single-mode fiber applications. It is 120mm long and 86mm wide. It is the same length as a 10G XENPAK optical transceiver but twice as wide. At the same time this optical transceiver has good thermal performance, making it in the process of using small power consumption.

Gigalight can provide several kinds of mainstream CFP optical transceivers: CFP 100GBASE-SR10, CFP 100GBASE-LR4, CFP2 100GBASE-SR10, CFP2 100GBASE-LR4, and 100GBASE-SR4 CFP4. Besides, it will release the latest 100G CFP2 ER4/100G CFP ER4 in January, 2018. These optical transceivers can achieve different transmission distances by connecting with different types of optical fibers.

Module Connector Transmission Distance
CFP 100GBASE-SR10 MPO 400M
CFP 100GBASE-LR4 Dual LC 10KM
CFP2 100GBASE-SR10 MPO 400M
CFP2 100GBASE-LR4 Dual LC 10KM
CFP4 100GBASE-SR4 MDIO 100M

The Origin and Application of 100G CFP Optical Module MSA

CFP MSA is the acronym for 100G Form factor Pluggable Multi-Source Agremment. In March 2009, the multi-source agreement was announced for the CFP module by Finisar, Opnext and Sumitomo to define high-speed Ethernet for 40G and 100G applications and support the next generation. In June 2010, CFP MSA ushers in a new member, AVGO, and released a multi-source agreement for a new version (Rev 1.4).

The CFP MSA introduces the block diagram of the CFP module. The DMUX and MUX in the optical part perform the optical demultiplexing and multiplexing. The WDM (wavelength division multiplexing) technology multiplexes the optical signals of multiple wavelengths onto a single-mode optical fiber for transmission. The module can work at ITU WDM wavelength. The module adopts the single fiber connection mode, which can save 2 × (N-1) optical fibers. In practical applications, the transmission distance of the single-mode optical fibers can reach more than 10km. In the schematic, N represents the number of optical channel, M represents the number of circuit channels. Generally, M and N are not equal. The electrical interface rate of the module is 10 Gbit / s. To implement 100 Gbps rate transmission, 10 electrical interfaces are required to support this. The number of electrical interfaces is 10 for the 100GBASE-LR4 and 100GBASE-ER4, and four for the 40GBASE-FR.

100G CFP Optical Module Hardware Definition

The CFP module has up to 148 pins, distributed at the bottom and top of the module’s electrical interface. The host computer can read the module control and status information through the electrical signal interface, which contains 6 control pins, 5 hardware alarm pins (including RX_LOS) and 8 MDIO management interface pins. Optical interface part may have SC, LC, and MPO connector form.

After accessing to the host, CFP optical modules can do the orderly timing switch according to the monitoring status. The timing diagram below is for the module in each steady-state and transient state signal associated with the flag switch.

CFP module operating temperature is not specified: 0 ℃ to 70 ℃. The module manufacturers need to test the performance of these modules in the two temperature conditions and have been to ensure that modules in the whole temperature range can reach the target requirements. The corresponding host also needs to provide the necessary cooling system to ensure that the module operates in this temperature range.

CFP SMA also defines the module size, weight, plug-in strength and so on, as well as the mainframe connected to the module of the various mechanical and electrical structures are detailed design. If you have any question or suggestion, welcome to visit our official website: Gigalight.

100G CFP/CFP2 LR4 Optical Transceivers: What’s the Key Technology?

The form factors of 100G CFP optical modules can be divided into CFP/CFP2/CFP4, and they can be divided into 100GBASE-SR10, 100GBASE-LR4, and 100GBASE-ER4 according to the transmission distance. All optical module transmission distance is decided by the optical output signal OSNR tolerance and chromatic dispersion tolerance decision. Generally speaking, it is determined by the laser and its drive performance.

At present, there are two types of optical modulation methods for implementing CFP 100GBASE-LR4 transmission in the mainstream market. One is a Direct Modulation Laser Modulation (DML) mode, that is, a direct modulation laser. And another one is an Electlro -Modulation Modulation (EML) mode, that is, modulation laser.

The following post will briefly introduce some key technical points of using the TEC circuit and EML modulation mode to realize the 100G CFP / CFP2 LR4 optical transceivers.

1. TEC Circuit

EML lasers need to work at a certain wavelength, the temperature jump will lead to a temperature drift effect, resulting in wavelength instability, drifting, so the stable working conditions of the laser is a relatively stable operating temperature (steady wavelength) This requires that we have to provide a high-precision TEC circuit, that is, a semiconductor refrigerator. The TEC is actually a PN junction made of two semiconductors of different materials. When a direct current passes through the PN junction, electrons and gaps in the two materials The hole produces an endothermic or exothermic effect during movement across the PN junction, effecting a cooling or heating laser effect, and TEC heating or cooling can be controlled by changing the current direction and size.

A high-precision op amp compares the target temperature we set with the temperature fed back by the thermistor, and the error voltage is amplified by a high-gain amplifier while compensating for the network’s contribution to the hot and cold ends of the laser The phase delay is compensated to drive the H-bridge output to control the size and direction of the TEC current. When the temperature drops below our target temperature, the H-bridge will reduce the TEC current or change the direction of the TEC current for cooling. Conversely, the final control loop Road will reach a dynamic equilibrium, the temperature will stabilize. Among them, the compensation circuit is the most critical part of the TEC temperature control circuit, that is PID proportional integral differential adjustment compensation network, which determines the TEC controller response speed and regulation accuracy.

2. EAM Regulation

EML lasers are essentially integrated devices for EAM (Electroabsorption Modulator) and LD (DFB lasers). The key core is the EML chip, which is the core of an electro-absorption modulated laser based on the Stark Effect (QCSE) design. The DML laser modulates the light intensity by directly controlling the laser current, which always works in an unstable state and is easily influenced by the outside world. In contrast, the EML laser mainly controls the optical signal by controlling the EAM, the light source will be more stable, and the transmission Relatively speaking, the characteristics and transmission effects will be better, especially in high frequency modulation and long distance.

In application, the LD pin injects a constant current to the laser to make the laser emit light, and the EAM changes the ratio of the laser light to obtain different intensity of light. The development of Ethernet technology has gone through a number of development stages from low speed to high speed.

The rate of development from 1M, 10M, 100M and 1G to 10G and 100G has led to more demand for it to evolve to a higher rate. I believe there will be new technologies have emerged to meet the growing demand for optical modules.

100G Optical Transceivers: Everything You Want to Know

As we all know, 100G is the future trend of network development. For the 100G optical transceivers market, the demand for 100G CFP optical transceivers in the telecom market in 2017 has increased by several times in the past year, and the follow-up demand for 100G optical transceiver solutions will also continue to increase. Before deciding to design a product or purchasing a 100G optical transceiver, you should understand the type and characteristics of the 100G optical transceivers to be able to make better judgments and choices. Here we will provide a comprehensive introduction about 100G optical transceivers for all of you.

100G Standard Introduction

100G interface standards include: SR4 (Short Reach), SR10, LR4 (Long Reach), ER4, ZR4; Among them, all the standard electrical signals are 1010G, For LR4 and ER4, the external optical signal is 425G. In addition, SR4 and SR10 are mainly used for short-distance transmission. The transmission distance does not exceed 100M. LR4, ER4 and CR4 are mainly used for long-distance transmission. LR4 transmission distance support 10KM, ER4 support 40KM. ZR4 supports 80KM.

100G Optical Transceiver Types

At present, the mainstream 100G optical transceiver models introduced on the market mainly include: CXP optical transceiver, CFP/CFP2/CFP4 optical transceiver and QSFP28 optical transceiver.

CXP:  

C for CXP represents 12 in hexadecimal, because CXP is a 12 full-duplex channel module with 12 * 10G transceivers. CXP is simple to implement, support hot-pluggable and has a smaller form factor than CFP. It supports 100GBASE-SR10 of the short-distance transmission. Under SR10 standard, it can interflow with CFP, CFP2, CFP4, and QSFP28 optical transceivers.

CFP Series (CFP / CFP2 / CFP4):

The C of 100G CFP optical transceiver stands for the number 100 (centum). It is a form factor pluggable optical transceiver, the volume is very large. CFP2 and CFP4 optical transceivers are smaller and smaller, CFP2 size is the half of the CFP half and the size of the CFP4 optical transceiver is one-half of the CFP2, supporting 40G / 100G. CFP4 optical transceiver width and power consumption has been greatly improved. The compact size is more suitable for high-density 100G Ethernet.

Note: CFP4 does not support the SR10 standard.

QSFP28 (Quad Small Form-factor Pluggable)

The 100G QSFP28 is implemented with 4 * 25 Gbps channels. In addition, the QSFP28 optical transceiver has an upgraded electrical interface that supports signals up to 28G and achieves the highest possible rate of 4 × 28 Gbit / s. 100G QSFP28 form factor sizes are smaller than the CFP4 optical transceiver, you can switch with high port density. Currently, there are four kinds of popular QSFP28 optical transceivers in the market based on different form factors: 100G QSFP28 CWDM4, 100G QSFP28 PSM4, 100G QSFP28 SR4 and 100G QSFP28 LR4. As the QSFP28 technology matures, the cost of the QSFP28 optical transceiver decreases, prompting the QSFP28 optical transceiver to become more and more popular.

CPAK:

The 100G form factor interface is introduced by Cisco, currently supporting 100GBASE-SR10, 100GBASE-SR4, and 100GBASE-LR4.

Types of 100G Optical Transceiver Connectors

Common connector types are: SC / LC / MPO and so on. The traditional 10G interface often use SC / LC connectors in the form of dual-core interconnect single-income hair. LC connector and SC connector are similar, but the LC connector is smaller than the SC.

MPO connector is a multiple fiber push-on / push-off all-in-one adapter. In simple terms, it is the use of parallel technology, the number of transponders in a box and the final combination of multiple optical fibers. MPO is divided into MPO12 and MPO24;

MPO 12 is 12 cores with 4 receivers and 4 transmissions, using 12 optical fibers, there are 4 idle, so the standard is SR4 / LR4.

The MPO 24 is a 24-core, 12-wire, 12-wire, 24-wire optical fiber soldered into 12-core arrays, one for transmit and one for receive. Take CFP as an example, in each array, the middle 10 * 10G optical fiber is used to transmit traffic, while the two optical fibers at both ends are idle. A total of four of the two arrays are idle, so the format is SR10. CXP module is 12 transmit and 12 receive, there is no idle line.

Take QSFP28 as an example, if the module inside uses splitters and multiplexers to 4 way 28g data modulated onto a fiber, the external transceiver is a single pay-single LC interface, so for long-distance can save fiber. This kind of optical fiber transmission technology with multiple optical fibers is called wavelength division multiplexing (WDM). Generally, short-distance uses MPO type, long-distance uses LC interface type for saving fiber.

How to Interoperate for Different 100G Optical Transceivers

The same type of 100G modules can communicate with each other. For example: CXP can interoperate with CXP; CFP-SR10 can interoperate with CFP-SR10. Different 100G module types can communicate with each other under the same standard and the same interface type. For example, CFP / CFP2 / CFP4 can communicate with the QSFP28 in the same signal system and the same interface type. For example, CFP2-LR4 with the duplex LC interface can interoperate with QSFP28-LR4 when the interface is duplex LC.

CXP module can interoperate with CFP / CFP2 / CFP4 / QSFP28 optical transceiver only when SR10 is adopted. When CXP and CFP2-SR10 are interoperated, the CXCPs must be screened out 1, 12, 13 and 24 at the edge of the CXP. Because CXP is 12 channels, CFP2 is 10 channels.

Conclusion

From the development trend, QSFP28 optical transceiver and CFP series optical transceiver are 100G network hot solutions, and the use of CXP will be less and less. The following table summarizes the commonly-used 100G optical transceiver types.

Types Standard The Largest Transmission Distance Connector Channel Wavelength Fiber Types
CXP SR10 100m MPO24 12*10G 850nm MMF
CFP/CFP2/CFP4(CFP4 doesn’t support SR10) SR10 100m MPO24 10*10G 850nm MMF
LR4 10km Dual LC 4*25G 1310nm SMF
ER4 40km Dual LC 4*25G 1310nm SMF
ZR4 80km Dual LC 4*25G 1310nm SMF
QSFP28 SR4 100m MPO12 4*25G 850nm SMF
LR4 10km LC 4*28G 1310nm SMF
ER4 40km LC 4*25G 1310nm SMF
ZR4 80km LC 4*25G 1310nm SMF
CWDM4 2km Dual LC 4*25G 1310nm SMF
PSM4 2km MPO 4*25G 1310nm SMF
CPAK (Cisco 100G) SR10/SR4/LR4 ~ ~ ~ ~ ~