The working principle and application of optical module in optical transmission

In the field of communication, electrical interconnection transmission of metal wires is greatly restricted due to factors such as electromagnetic interference, inter-code crosstalk and loss, and wiring costs.

As a result, optical transmission was born. Optical transmission has the advantages of high bandwidth, large capacity, easy integration, low loss, good electromagnetic compatibility, no crosstalk, light weight, small size, etc., so optical output is widely used in digital signal transmission.

Basic structure of optical module

Among them, the optical module is the core device in optical fiber transmission, and its various indicators determine the overall performance of the transmission. The optical module is a carrier used for transmission between the switch and the device, and its main function is to convert the electrical signal of the device into an optical signal at the transmitting end. The basic structure consists of two parts: “light emitting component and its driving circuit” and “light receiving component and its receiving circuit”.

The optical module contains two channels, namely the transmitting channel and the receiving channel.

The composition and working principle of the transmitting channel

The transmitting channel of the optical module is composed of an electrical signal input interface, a laser drive circuit, an impedance matching circuit and a laser component TOSA.

Its working principle is the electrical interface input of the transmitting channel, the coupling of the electrical signal is completed through the electrical interface circuit, and then the laser driving circuit in the transmitting channel is modulated, and then the impedance matching part is used for impedance matching to complete the modulation and drive of the signal, and finally Send the laser (TOSA) electro-optical conversion into optical signal for optical signal transmission.

The composition and working principle of the receiving channel

The optical module receiving channel consists of the optical detector component ROSA (composed of photodetection diode (PIN), transimpedance amplifier (TIA)), impedance matching circuit, limiting amplifier circuit and electrical signal output interface circuit.

Its working principle is that the PIN converts the collected optical signal into an electric signal in a proportional manner. TIA converts this electric signal into a voltage signal, and amplifies the converted voltage signal to the required amplitude, and transmits it to the limiter through the impedance matching circuit The amplifier circuit completes the re-amplification and reshaping of the signal, improves the signal-to-noise ratio, reduces the bit error rate, and finally the electrical interface circuit completes the signal output.

Application of optical module

As the core device for photoelectric conversion in optical communications, optical modules are widely used in data centers. Traditional data centers mainly use 1G/10G low-speed optical modules, while cloud data centers mainly use 40G/100G high-speed modules. With new application scenarios such as high-definition video, live broadcast, and VR driving the rapid growth of global network traffic, in response to future development trends, emerging application requirements such as cloud computing, Iaa S services, and big data put higher requirements on data center internal data transmission , Which will give birth to optical modules with higher transmission rates in the future.

Generally, when we choose optical modules, we mainly consider factors such as application scenarios, data transmission rate requirements, interface types, and optical transmission distances (fiber mode, required optical power, center wavelength, laser type) and other factors.