What parameters do you need to confirm when purchasing an optical module?

When selecting an optical module, you need to consider not only the stability and reliability of the optical module, but also its price and quality, compatibility with network devices, and data transmission requirements. Here, ETU-LINK introduces the optical module parameters that you should explain to the manufacturer when you select an optical module. I hope this will be helpful to you.

1. Interface rate

When selecting the rate of an optical module interface, you need to confirm the rate supported by the switch port, and then select the rate of the optical module based on the rate supported by the switch.

The rates of optical modules are FE(155M), GE(1.25G), 10GE, 25GE, 40GE, 100GE, and 400GE. In addition, Fibre Channel is commonly used in storage networks (SAN) with 8G, 16G rate (Brocade devices are more used).

2. Transmission distance

Optical modules with different rates, wavelengths, or packages support different transmission distances. Therefore, it is important to determine the transmission distances. For example, the SFP-10G-SR 10-gigabit multi-touch optical module can only reach 300m, while the SFP-10G-ZR 10-gigabit single-touch optical module can reach 80km.

Optical modules at different distance specifications have different luminous sizes. Note that (during field tests), the transmitted optical power of a long-distance optical module is generally greater than the overloaded optical power. Therefore, pay attention to the length of the optical fiber to ensure that the actual received optical power is smaller than the overloaded optical power.

If the length of an optical fiber is short, use the long distance optical module in conjunction with the optical attenuation (dB/km) of the optical fiber to avoid burning out the peer optical module.

3. Optical fiber type

Optical fibers can be classified into single-mode optical fibers and multi-mode optical fibers. The center wavelength of a single-mode optical module is generally 1310nm or 1550nm, and is used together with single-mode optical fibers. Single-mode optical fiber transmission frequency band wide, large transmission capacity, suitable for long distance transmission.

The center wavelength of a multi-mode optical module is 850nm and is used with multi-mode optical fibers. Multi-mode fiber has mode dispersion defect, its transmission performance is worse than single-mode fiber, but its cost is low, and it is suitable for small capacity and short distance transmission.

4. Optical fiber interface

Common module interfaces include LC,SC,MPO, etc., but the project cost and future upgrade and expansion need to be comprehensively considered. For example, the 40G QSFP+ multi-touch interface is usually an MPO interface. Using MPO jumpers, the optical module cost is low, but the cost of laying MPO jumpers is high.

The 40G QSFP+ is also available with LC interface specifications and uses LC jumpers, so the cable laying cost is lower. So it's a matter of making a comprehensive decision based on the actual situation.