What is BIDI optical module?


Most of the optical modules on the market currently transmit data through two optical fibers. One optical fiber is used to receive data from the network device, and the other optical fiber is used to transmit data to the network device. However, there is a kind of optical module that can realize data transmission with only one optical fiber. This kind of optical module is BiDi.

1、Basic knowledge of BiDi optical module

BiDi (bidirectional) single-fiber bidirectional optical module is different from the general two-port (TX transmitting end and RX receiving port) optical module, it has only one fiber port, using WDM technology, sending and receiving different center wavelengths in two directions , So as to realize the optical fiber bidirectional transmission of optical signals.

2、Working principle of BiDi optical module

The BiDi optical module is equipped with a wavelength division multiplexing (WDM) coupler, also called a duplexer, which simultaneously completes the transmission of 1310nm optical signals and the reception of 1550nm optical signals, or vice versa. Therefore, in order to operate effectively, BiDi optical modules must be used in pairs. By tuning the duplexer to match the desired wavelength of the transmitter and the receiver, the operating wavelengths of the two duplexers must be complementary and consistent. For example, if the paired BIDI optical module is connected to device A (upstream) and device B (downstream), then: the duplexer of optical module A must have a receiving wavelength of 1550nm and a transmitting wavelength of 1310nm. The duplexer of optical module B must have a reception wavelength of 1310nm and an emission wavelength of 1550nm.

3、Classification of BiDi optical modules

BiDi SFP optical module

It is usually used in a high-performance integrated duplex data link through a single optical fiber. The rate is 144M-4.25Gbps. If the transmission distance is within 40km, the wavelength scheme of BiDi SFP optical module is 1310nm/1550nm, 1310nm/1490nm; if the transmission distance is above 40km, the wavelength scheme of BiDi SFP optical module is 1550nm/1490nm.

BiDi SFP+ optical module

BiDi SFP+ optical module is an enhanced SFP optical module. It is used in the bidirectional 10G serial optical communication of 1330/1270nm transmitter and 1270/1330nm receiver, with a maximum transmission distance of 60KM.

BiDi XFP optical module

BiDi XFP optical module is an XFP MSA packaged optical module with built-in digital diagnostic function. Its emission wavelength and reception wavelength are 1330nm/1270nm and 1270nm/1330nm respectively. It is generally used together with strip SMF, and the maximum transmission distance can reach 10km. In addition, the power consumption of BiDi XFP optical modules is less than 2W, which is used in 10G Ethernet. BIDI X2 optical module.

BiDi X2 optical module

BiDi X2 optical module is used in two-way 10G serial optical communication, and this optical module is composed of two parts: the transmitter part uses 1330/1270nm DFB laser. The receiver part uses integrated 1270/1330nm preamplifier and post amplifier.

BiDi QSFP+SR4 optical module

40G QSFP+ BiDi SR4 only needs two 20G channels to achieve 40G transmission. Each channel can transmit and receive signals from a multi-mode cable, but it should also be noted that 40G QSFP+ BiDi SR4 must be used in pairs.

The 40G QSFP+ BiDi SR4 first combines four electrical signals with two 20G electrical signals, exchanges the two 20G electrical signals into two 20G optical signals of different wavelengths, and transmits the 20G optical signals of different wavelengths to an optical cable, and then 40G The device receives the light signal and works.

The commonly used wavelengths of 40G QSFP+ BiDi SR4 optical modules are 850nm and 900nm, which can be used for stable transmission in multimode optical fiber systems. In addition, the transmission distance using OM3 patch cords is 100m, and the transmission distance using OM4 patch cords is 150m.

4、BiDi optical module and ordinary two-way optical fiber module

1、The single-fiber bidirectional optical module adopts WDM technology, and the dual-fiber bidirectional optical module is not used;

2、Single-fiber bidirectional optical modules need to be used in pairs, while dual-fiber bidirectional optical modules are not required;

3、The structure of a single-fiber bidirectional optical module is more complicated than that of a dual-fiber bidirectional optical module, and a splitter combiner must be introduced on the optical module;

4、Only one optical fiber is required between single-fiber bidirectional optical modules, and two dual-fiber bidirectional optical modules are required.


Single-fiber BiDi optical modules are more expensive, but save fiber resources and only need one fiber, which is a better choice for users with insufficient fiber resources. The structure of the single-fiber BiDi optical module is more complicated than that of the ordinary dual-fiber bidirectional optical fiber module, and the optical splitter and combiner need to be introduced on the optical module.

Dual-fiber optical modules do not need to be paired. Any two optical modules can be connected. The price is cheaper than single-fiber BIDI optical modules, but one more optical fiber is required. If the fiber resources are sufficient, you can choose dual-fiber optical modules.

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