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How do you select the optical module parameters?

Number of visits: Date:2017-07-17

The hardware development engineer, optical module has a lot of very important technical parameters, but for GBIC and SFP these two kinds of hot pluggable optical module, optical module only needs to know the following 3 main parameters can work smoothly:

First, central wavelength: unit nanometer (nm), there are 3 main kinds at present:

1) 850nm (MM, multi-mode, low cost, but short transmission distance, generally can only transmit 500M);

2) 1310nm (SM, single-mode) with large losses but small dispersion during transmission, generally used for transmission within 40KM);

3) 1550nm (SM), single-mode, transmission in the process of small losses, but large dispersion, generally used for long distance transmission over 40KM, the farthest can be no

Relay direct transmission 120KM);

Second, transmission rate: refers to the number of bits per second to transmit data (bit), unit BPs, there are 4 commonly used: 155Mbps,

1.25Gbps, 2.5Gbps, 10Gbps and so on. The transmission rate is generally downward compatible, so the 155M optical module is also called FE (Bai Zhao) optical module, and the 1.25G optical module, also called GE (Qian Zhao) optical module, is the most widely used module in the optical transmission equipment. In addition, in fiber storage systems (SAN), the transmission rates are 2Gbps, 4Gbps and 8Gbps;

Third, transmission distance: refers to the optical signal, no need to relay amplification can direct transmission distance, unit kilometers (also known as kilometers, KM), optical mode

The block has the following specifications: multi-mode 550m, single mode 15km, 40km, 80km and 120km, etc., as detailed in the first instruction.

Other concepts of optical module:

In addition to the above 3 main technical parameters, the optical module has the following basic concepts. These concepts need to be understood simply:

1) laser type: laser is the most core device in optical module. It injected current into semiconductor material and injected laser through photon oscillation and gain of resonator. At present, the most common lasers are FP and DFB lasers. Their differences are that semiconductor materials and resonators are different in structure, and the price of DFB lasers is much higher than that of FP lasers. The transmission distance is generally use FP laser in optical module within 40KM optical module; 40KM transmission distance = using DFB laser;

2) loss and dispersion: loss is the loss of light energy due to absorption, scattering and leakage of light when light is transmitted in the fiber. This energy is dissipated at a certain rate with the increase of the transmission distance. Dispersion arises because different wavelengths of the electromagnetic wave propagation in a medium speed range, resulting in different wavelength components of the optical signal due to the cumulative transmission distance in different time at the receiving end, resulting in the pulse, and cannot distinguish the signal value. Transmission distance of the optical module of the main effects of the two parameters, in the actual application process, 1310nm optical module according to the general 0.35dBm/km calculation of link loss, 1550nm optical module according to the 0.20dBm/km calculation of link loss, calculation of dispersion value is very complex, usually only for reference;

3) transmit light power and receive sensitivity: the transmitted light power refers to the output light power of the optical module sending end light source, and the receiving sensitivity refers to the minimum receiving light power of the optical module at a certain rate and bit error rate. The two parameters of the unit are dBm (meaning DBM, logarithmic form power unit MW formula 10lg, 1MW converted to 0dBm), the transmission distance is mainly used to define the product, optical module of different wavelengths, the transmission rate and the transmission distance of the optical transmission power and receiver sensitivity will be different, as long as you can to ensure the transmission distance on the line;

4) optical module life: international standard, 7 * 24 hours of continuous work 50 thousand hours (5 years);

5) fiber optic interface: SFP optical module is LC interface, GBIC optical module is SC interface, and other interfaces such as FC and ST;

6) operating temperature: 0~+70 DEG C; storage temperature: -45~+80 DEG C; working voltage: 3.3V; working level: TTL/PECL/CML/LVDS.

TypeInfo: Industry news

Keywords for the information:optical module 

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