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ICT

Optical Transceiver Module plays the role of photoelectric conversion in optical communication network. It is composed of opto-electronic devices, functional circuits and optical interfaces. The most important parts of optical transceiver modules are Laser Emitting and Laser Receiving devices. The Laser Emitting part of optical transceivers is called TOSA (Transmit Optical Sub-Assembly), its key device is Laser Diode; the Laser Receiving part is called ROSA (Receiver Optical Sub-Assembly), the key device is Photo Diode. Optical Transceivers are BOSA (Bi-directional Optical Sub-Assembly) Assemblies and packaged with Laser Diode and Photo Diode together. TOSA (Transmit Optical Sub-Assembly) and ROSA (Receiver Optical Sub-Assembly) are essential components in the uni-directional transceivers. Laser Diodes(LD), the key emitting devices of optical transceivers, have FP, DFB, VCSEL, EML types, etc. Generally, the laser diode (LD Chip), backlight detection tube (PIN PD Chip), thermistor, TEC cooler and optics are integrated in the package. Components include collimation mechanism and more.

Optical Transceiver Chips  Optical transceiver chips are mainly divided into laser diode chips and photo diode chips, respectively used in laser diodes (such as VCSEL, DFB, EML) for converting electrical signals into optical signals at the transmission end, and in photo diodes (such as PIN, APD) for converting optical signals into electrical signals at the receiver end. They are assembled with filters, metal caps, ceramic tubes and some other components into TOSA, ROSA, or BOSA, and then packaged with PCB, electronic chips and some other sub-assemblies into optical transceiver modules. Optical chips are the core element in optical transceivers. Its performance directly determines attributes including the transmission rate, temperature drift, operation stability and signal-to-noise ratio of optical transceiver modules. In terms of cost, optical chips and sub-assemblies take up 50% to 70% of the total cost of optical transceiver modules, tunable laser, etc. Passive Optical Component Chips Optical Laser chips are also used in passive optical components mainly include PLC (Planar Lightwave Circuits) optical splitter chips and AWG (Array Waveguide Grating) chips. PLC optical splitter chips are usually made of two kinds of technology, silicon dioxide optical waveguide and glass optical waveguide. It is composed of multiple branches cascaded to realize the coupling, branching and distribution of optical signals. AWG chips are composed of two multiport couplers and connected array waveguides, to realize wavelength division multiplexing of N*1, wavelength division demultiplexing of 1*N and wavelength routing of N*N, etc. It is widely used in WDM optical module, ROADM and WSS. Application Scenarios Optical/Laser chips emit light based on the principle of stimulated emission and can divided into surface-emitting type and edge-emitting type. Surface-emitting type mainly refers to VCSEL (Vertical Cavity Surface-Emitting Laser), suitable for short-distance multi mode application. Edge-emitting type mainly includes FP (Fabry-Perot laser), DFB (Distributed Feedback Laser) and EML (Electro-Absorption Modulated Laser). FP is suitable for application of short to medium reach below 10G, while DFB and EML are suitable for high speed data rate on medium to long reach. EML is currently the main light source for achieving single channel rate of 50G and above, by integrating EAM (Electro-Absorption Modulator) to DFB. Photo diode chips include two main types: PIN(Positive-Intrinsic-Negative Photo Diode) and APD(Avalanche Photo Diode). The former has relatively low sensitivity and is applied to medium and short reach, while the latter has high sensitivity and is applied to medium and long distance.