What are the common parameters of optical modules

For hardware development engineers, optical modules must be no strangers. However, I believe that many friends do not know much about the common parameters and basic knowledge of optical modules. Let's talk about the common parameters of optical modules and the basic knowledge of optical modules.

ZR Cable Optical Module

What are the common parameters of optical modules

First, the central wavelength: unit nanometer (nm), there are currently three main types:

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

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

3) 1550nm (SM, single-mode, small loss but large dispersion during transmission, generally used for long-distance transmission over 40KM, up to 120KM can be directly transmitted without relay);

Second, the transmission rate: refers to the number of bits (bit) of data transmitted per second, in bps, there are currently four commonly used: 155Mbps, 1.25Gbps, 2.5Gbps, 10Gbps, etc. The transmission rate is generally backward compatible, so the 155M optical module is also called FE (100M) optical module, and the 1.25G optical module is also called GE (Gigabit) optical module, which is the most widely used module in optical transmission equipment at present. In addition, in the optical storage system (SAN), its transmission rate is 2Gbps, 4Gbps and 8Gbps;

Third, transmission distance: refers to the distance that optical signals can be directly transmitted without repeater amplification, in units of kilometers (also called kilometers, km). Optical modules generally have the following specifications: multi-mode 550m, single-mode 15km, 40km, 80km and 120km, etc., see the first description for details.

What are the basic knowledge of optical modules

In addition to the above three main technical parameters, the optical module has the following basic concepts, which only need a simple understanding:

1) Laser category: The laser is the core device in the optical module. It injects current into the semiconductor material and emits laser light through the photon oscillation and gain of the resonator. At present, the most commonly used lasers are FP and DFB lasers. The difference between them is the semiconductor material and cavity structure. The price of DFB lasers is much more expensive than that of FP lasers. Optical modules with a transmission distance of less than 40KM generally use FP lasers; optical modules with a transmission distance of ≥40KM generally use DFB lasers;

2) Loss and dispersion: Loss is the loss of light energy due to absorption, scattering and leakage of the medium when light is transmitted in the optical fiber. This part of the energy is dissipated at a certain rate with the increase of the transmission distance. Dispersion is mainly caused by the fact that electromagnetic waves of different wavelengths travel in the same medium at different speeds, resulting in different wavelength components of the optical signal reaching the receiving end at different times due to the accumulation of transmission distances, resulting in pulse broadening and inability to distinguish the signal. value. These two parameters mainly affect the transmission distance of the optical module. In the actual application process, the link loss of the 1310nm optical module is generally calculated at 0.35dBm/km, and the link loss of the 1550nm optical module is generally calculated at 0.20dBm/km. The calculation of the dispersion value Very complex, generally for reference only;

3) Transmitting optical power and receiving sensitivity: Transmitting optical power refers to the output optical power of the light source at the transmitting end of the optical module, and receiving sensitivity refers to the minimum received optical power of the optical module at a certain rate and bit error rate. The units of these two parameters are both dBm (meaning decibel milliwatts, the logarithmic form of the power unit mw, the calculation formula is 10lg, and 1mw is converted to 0dBm), which are mainly used to define the transmission distance of the product, different wavelengths, transmission rates and The optical transmission power and receiving sensitivity of the optical module of the transmission distance will be different, as long as the transmission distance can be ensured;

4) The service life of the optical module: the international unified standard, 7Х24 hours of uninterrupted work for 50,000 hours (equivalent to 5 years);

5) Optical fiber interface: SFP optical modules are all LC interfaces, GBIC optical modules are SC interfaces, and other interfaces include FC and ST;

6) Working temperature: 0~+70℃; Storage temperature: -45~+80℃; Working voltage: 3.3V; Working level: TTL/PECL/CML/LVDS.

The above is the full content of the common parameters of optical modules and the basic knowledge of optical modules. I believe you have a more comprehensive understanding of optical modules here, and hope to give you some help.