1.25g optical module is a gigabit module. 1.25G optical module is also known as GE (Gigabit) optical module, that is, optical transceiver module, the English name OpticalModle. optical module is usually composed of optical transmitter devices (TOSA, including lasers), optical receiver devices (ROSA, including photodetectors), functional circuits, and optical (electrical) interfaces and other components.

The transmitting part of 1.25g optical module is: the input electrical signal of a certain code rate is processed by the internal driver chip to drive the semiconductor laser (LD) or light-emitting diode (LED) to emit the corresponding rate of modulation of the optical signal, which is equipped with the internal optical power automatic control circuit, so as to make the output of the optical signal power to maintain a stable.

1.25g optical module receiving part is: a certain code rate of the optical signal input module by the light detection diode converted to electrical signals. After the preamplifier output the corresponding code rate of the electrical signal, the output signal is generally PECL level. At the same time in the input optical power is less than a certain value will output an alarm signal.

Optical module has a lot of important photoelectric technology parameters, but for the GBIC and SFP these two hot-swappable optical module, the selection of the most concerned about the following three parameters:

1, the center wavelength: unit nanometer (nm), there are currently three main types: 850nm (MM, multi-mode, low cost but short transmission distance, generally only 500M transmission); 1310nm (SM, single mode, the transmission process loss is large but the dispersion is small, generally used for transmission within 40KM); 1550nm (SM, single mode, the transmission process loss is small but the dispersion is big, generally used for 1550nm (SM, single mode, small loss but large color dispersion during transmission, generally used for long-distance transmission above 40KM, the farthest can be directly transmitted without relay 120KM).

2, transmission rate: the number of bits of data transmitted per second (bit), the unit bps. Currently there are four commonly used: 155Mbps, 1.25Gbps, 2.5Gbps, 10Gbps, 25Gbps, 40Gbps, 100Gbps and so on. The transmission rates are generally backward compatible, so the 155M optical module is also known as FE (100 Gigabit) optical module, and the 1.25G optical module is also known as GE (Gigabit) optical module, which is currently the most widely used module in optical transmission equipment. In addition, in the fiber optic storage system (SAN) in its transmission rate of 2Gbps, 4Gbps and 8Gbps.

3, transmission distance: optical signals without relay amplification can be directly transmitted distance, unit kilometers (also known as kilometers, km). Optical modules generally have the following specifications: multi-mode 550m, single-mode 15km, 40km, 80km and 120km and so on.

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