The Optical Transceiver is the core device of optical communication. It mainly performs the conversion between the optical signal and the electrical signal.
The Optical Transceiver is composed of optoelectronic devices, functional circuits and optical interfaces, among which the optoelectronic devices are divided into The receiving part and the transmitting part are two parts, and the receiving part realizes the transformation of the optical power conversion, and the transmitting part mainly realizes the conversion of the electric light conversion.
Receiving part: inputting the optical signal of a certain code rate into the module and then converting it into an electric signal by the photo detecting diode, and outputting the electric signal of the corresponding bit rate after the preamplifier, and the output signal is generally PECL level. At the same time, an alarm signal is output after the input optical power is less than a certain value.
Transmitting part: an electric signal inputting a certain code rate is processed by an internal driving chip to drive a semiconductor laser (LD) or a light emitting diode (LED) to emit a modulated light signal of a corresponding rate, and an optical power automatic control circuit (APC) is internally provided therein. To keep the output optical signal power stable.
The role of the Optical Transceiver
The function of the Optical Transceiver is to complete the conversion between the photoelectric signals, mainly as a carrier for transmission between the switch and the device, and the transmitting end converts the electrical signal into an optical signal, and after 
transmitting through the optical fiber, the receiving end converts the optical signal into an electrical signal.
The current state of the data center:
1, the traditional 10G often uses SFP + Optical Transceivers, two-core LC interface interconnection;
2, 40G Ethernet specification requires 8-core interconnection, 4 transmission and 4 reception, using 12-core optical cable cabling solution, each channel has 4 dedicated transmitting fibers and 4 dedicated receiving fibers, and the middle 4 fibers remain idle;
3, 100G Ethernet common solution specifies the use of 24 optical fibers, divided into two 12-core arrays, one array dedicated to transmission, another array dedicated to receiving, 10 optical fibers in the middle of each array for transmission of traffic, and two ends 2 fibers are idle.
Type of long distance Optical Transceiver:
Long-range Optical Transceivers are available in SFP Optical Transceivers, SFP+ Optical Transceivers, XFP Optical Transceivers, 25G Optical Transceivers, 40G Optical Transceivers, and 100G Optical Transceivers. Among them, the long-distance SFP+ Optical Transceiver adopts the EML laser component and the photodetector component to reduce the power consumption of the Optical Transceiver and improve the accuracy; the long-distance 40G Optical Transceiver adopts a driver and a modulation unit in the transmitting link, and adopts a receiving link in the receiving link. The optical amplifier and photoelectric conversion unit realize a maximum transmission distance of 80 km.
Classification of short-range Optical Transceivers
1.10GBASE-SR Optical Transceiver
The 10GBASE-SR Optical Transceiver uses a duplex LC connector, which is generally used together with multimode fiber. Its wavelength is 850nm, which is used for short-distance transmission of 10G networks. The distance transmitted by the 10GBASE-SR Optical Transceiver varies according to the type of multimode fiber used. For example, when using OM3 fiber, the transmission distance can reach 300m, while when using OM4 multimode fiber, the transmission distance can reach 400m.
2.40GBASE-SR4 Optical Transceiver
The 40GBASE-SR4 Optical Transceiver uses a 12-pin MPO/MTP connector, which is typically used with multimode fiber and has a wavelength of 850 nm. The 40GBASE-SR4 Optical Transceiver uses four multimode fiber channels with a transmission rate of 10G to achieve 40G short-distance transmission. The 40GBASE-SR4 Optical Transceiver uses different transmission distances when used with different multimode fibers. For example, when used with OM3 fiber, the transmission distance is 100m, and when used with OM4 fiber, the transmission distance is 50m.
3.100GBASE-SR10 Optical Transceiver
The package type of the 100GBASE-SR10 Optical Transceiver is CFP. It is generally used together with multimode fiber. The 100GBASE-SR10 Optical Transceiver is the same as the 40GBASE-SR4 Optical Transceiver. When used with OM3 multimode fiber, the transmission distance is 100m, and the OM4 multimode. When the fiber is used together, the transmission distance is 50m.
The difference between short-distance Optical Transceivers and long-distance Optical Transceivers
- The transmission distance is different
The transmission distance of short-distance Optical Transceivers is generally less than 2km, while the transmission distance of long-distance Optical Transceivers is generally more than 30km.
- The fiber types of are different
The short-distance Optical Transceiver is generally connected to a multimode fiber with a fiber diameter of 50/125 um or 62.5/125 um for data transmission, and the long-distance Optical Transceiver is a single-mode fiber with a fiber diameter of 9/125 um. 
- The wavelengths of are different
Short-range Optical Transceivers typically have a wavelength of 850 nm, while long-haul Optical Transceivers typically have a wavelength of 1550 nm.
- The scope of application of the two is different
The short-distance Optical Transceiver is suitable for short-distance transmission, such as the server room server, and the long-distance Optical Transceiver is suitable for long-distance transmission, such as metropolitan area network construction.
