The Key Technology for 100G CFP/CFP2 LR4 Optical Transceiver

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.


Advantages of 100G CFP4 Optical Transceivers

With the network market gradually develop from 10G to 40G and 100G, 40G/100G optical devices are also widely used in various fields. In the next few years, 100G products will continue to be popularized and gradually accepted by the market. 100G CFP series optical transceivers are available in three different package sizes: CFP, CFP2, CFP4 optical transceivers.

The 100G CFP optical transceiver is also known as 100G client module, which is a form factor pluggable module that supports hot plugging. CFP series of optical transceivers from the launch to now experienced a total of CFP, CFP2 development, and now, CFP4 optical transceiver has been successfully introduced and widely acclaimed. Compared with CFP / CFP2 optical transceiver, 100G CFP4 optical transceiver has the same rate but the transmission efficiency has greatly improved. Besides, the power consumption is reduced and the cost is lower than CFP2. CFP4 optical transceiver has irreplaceable advantages. We will talk about it in the second part.

Advantages of CFP4 Optical Transceiver:

Compared with the traditional CFP, CFP2 series, CFP4 optical transceiver has obvious advantages.

Smaller size: CFP4 optical transceiver is one-half of that of CFP2, which is one quarter of CFP. It is the smallest optical transceiver in CFP series optical transceiver.

Higher transmission efficiency: The early 100G CFP optical transceiver in 10 * 10 mode, through 10 10G channels, to 100G transmission rate, but the current 100G CFP4 optical transceiver with 4 * 25 mode, through 4 25G channel, to achieve 100G transmission, transmission more efficient and more stable.

Module integration is higher: CFP2 integration is 2 times CFP, CFP4 integration is four times CFP.

Lower power consumption and cost: CFP4 optical transceiver is compatible with MSA protocol and supports the same speed as CFP2 and CFP2s. The transmission efficiency is obviously improved, but the power consumption drops drastically, only about half of the original, and the system cost is more than that of CFP2 low.

As we all know, 100G is the future trend of network development. With the expansion of the 100G industry, the cost of a 100G optical transceiver will also be reduced correspondingly, thereby reducing the cost of deploying the entire 100G network. Gigalight believes that CFP4 series optical transceivers for 100G applications brought will promote the 100G faster development. 


How Much Do You Know about 100G Optical Transceivers

In recent years, with the rapid growth of users' demand for transmission links of 40G and 100G optical transceivers, cloud computing, mobile broadband and IPTV users have also increasingly requested bandwidth. 40G links have been deployed for several years now and 40G optical transceivers are ubiquitous in the data center. In the past two years, 100G optical transceivers have been rapidly developed in the Data Center market due to the development of optical industry centered on "100G network deployment." At present, 100G optical transceivers on the market mainly include: CXP optical transceiver, CFP optical transceiver, CFP2 optical transceiver, CFP4 optical transceiver and QSFP28 optical transceiver. Here we are going to introduce you the several main types of 100G optical transceivers. How much do you know about 100G optical transceivers? The post may give you an answer.

 1. CXP Optical Transceiver

CXP optical transceiver transmission rate is up to 12 × 10Gbps and supports hot swappable. "C" stands for 12 in hexadecimal, Roman "X" stands for 10 Gbps for each channel, and "P" for a hot pluggable pluggable. The CXP optical transceivers are targeted at the high-speed computer market and complement the CFP optical transceivers in Ethernet data centers. Technically, CFP optical transceivers and multimode fiber are both used for short-distance data transmission. Since multimode fiber markets require high-density panels, their dimensions have not been truly optimized in the multimode fiber market.

CXP optical transceiver is 45 mm long and 27 mm wide. It has a larger size than XFP optical transceiver or CFP optical transceiver and therefore it provides a higher density network interface. In addition, CXP optical transceiver is a copper connector system designated by the Wireless Broadband Trade Association that supports 12 ports for 100 GbE, 3 10G link for 40 GbE or 12 10GbE Fiber Channel or 12 × QDR link transmission of wireless broadband signals.

2. CFP / CFP2 / CFP4 Optical Transceiver

The CFP Multi-Source Agreement (MSA) defines the requirements for hot-pluggable optical transceivers that are used for 40G and 100G network transmission, including next-generation high-speed Ethernet (40GbE and 100GbE). CFP optical transceiver supports transmission on a single-mode and multi-mode fiber at a variety of rates, protocols, and link lengths, including all the physical media dependent (PMD) interfaces in the IEEE 802.3ba standard. 100G network has three PMDs: CFP 100GBASE-SR10 can transmit 100m, CFP 100GBASE-LR4 can transmit 10km, CFP 100GBASE-ER4 can transmit 40km.

CFP optical transceiver is based on the Small Form Factor Pluggable Optical transceiver (SFP) interface and is larger in size to support 100Gbps data transmission. The electrical interface for the CFP optical transceiver uses 10 x 10 Gbps channels for transmission in each direction (RX, TX) and therefore supports 10 x 10 Gbps and 4 x 25 Gbps interworking. CFP optical transceiver can support a single 100G signal, OTU4, one or more 40G signals, OTU3 or STM-256 / OC-768.

Although CFP optical transceiver can achieve 100G data applications, but its large size can no longer meet the needs of high-density data center. In this case, the CFP-MSA committee defines two other forms: CFP2 and CFP4 optical transceivers. The figure below shows the size comparison of CFP, CFP2 and CFP4 optical transceivers:

3. QSFP28 Optical Transceiver

Similarly, as a small size 100G optical transceiver, QSFP28 optical transceiver is also receiving more and more attention. As its name implies, the QSFP28 optical transceiver has the same design philosophy as the QSFP optical transceiver. The first generation QSFP optical transceiver has four Tx and Rx ports with a rate of 10 Gbps per channel. For QSFP28 optical transceivers, QSFP optical transceivers can send and receive up to 28 Gbps of data per channel. Compared with CFP4 optical transceiver, QSFP28 optical transceiver size is smaller than CFP4 optical transceiver only. Although the QSFP28 optical transceiver offers a density advantage over the CFP4 optical transceiver, the higher maximum power consumption of the CFP4 optical transceiver gives it an advantage over longer distances for optical transmission. There are many kinds of 100G QSFP28 optical transceivers in the market, among them; QSFP28 CWDM4 and QSFP28 PSM4 are the latest most popular optical transceiver modules that are widely used for Data Center.


4. CPAK Optical Transceiver

There is another 100G optical transceiver called CPAK on the market. The CPAK optical transceiver is the new module type popular this year. The appearance is similar to the Cisco optical transceiver, but the interface uses the IEEE standard and supports compatibility with other interfaces.

100G optical transceivers are available in a wide range of options. In addition, 100G AOC (Active Optical Cable) will also be introduced to the market for short-distance interconnection and 100G migration applications, which will challenge 100G optical transceivers. At the same time, with the rapid development of technology, 100G optical transceivers will become more cost-effective, and 100G network applications will be getting closer and closer to us. For more details about 100G optical transceivers, please contact us.