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Learn more about optical modules

█ What parts does the optical module consist of?

An optical module is usually composed of a light emitting component (including a laser), a light receiving component (including a detector), a driving circuit, and a photoelectric interface, etc. The structure is shown in the figure below.



Schematic diagram of the optical module structure (SFP+ package) (the picture comes from the optical module white paper)


█ What is the function of the optical module?

In optical communication, the transmission and reception of information are realized by optical modules:

  1. At the sending end, the optical module completes the electrical/optical conversion.
  2. Light travels in an optical fiber.
  3. At the receiving end, the optical module realizes optical/electrical conversion.



The function of the optical module



█ For 5G, where is the optical module used?

The optical module is the basic unit of the physical layer of the 5G network and is widely used in wireless and transmission equipment.

For 5G bearer, 25/50/100 Gb/s high-speed optical modules will be gradually introduced in the access layer of fronthaul, midhaul and backhaul, and N×100/200/400 Gb/s high-speed optical modules will be layer import.


█ What is the development trend and technical route of optical modules?

The development trend and technical route of optical modules are shown in the figure below.






█ What is the package of the optical module?


The package form is the most important feature of the optical module.

The determination of the packaging form standard enables the optical modules produced by various manufacturers to be compatible and interconnected.

With the development of optoelectronic devices, device and chip bandwidths are gradually increasing. The bandwidth of devices and chips has increased, and with the development of photonic integration technology, optical modules have also achieved higher rate transmission and smaller size packaging.

The figure below shows the development of the optical module packaging form.




█ How does the optical module increase the transmission rate?

High-speed data transmission makes various applications of 5G possible.

Transmission rate refers to the number of bits transmitted per second, in Mb/s or Gb/s. Optical modules have gradually increased from the early 155 Mb/s: 622 Mb/s, 1.25Gb/s, 2.5Gb/s, 10Gb/s, 25, 50, 100 Gb/s, 200 Gb/s, 400 Gb/s , 800 Gb/s.

In order to achieve a higher rate, there are usually the following three solutions:




█ What do DR, LR, and ER in the transmission distance of optical modules mean?

In the field of optical communication, faster and farther has always been the relentless pursuit of communication people.

The transmission distance of optical modules mainly includes SR (100 m), LR (10 km), ER (40 km), and ZR (80 km) in the early stage.

With the construction of the data center network, two transmission distances, DR (500 m) and FR (2 km), have been further derived for more cost-effective wiring.

Common optical module transmission distances are as follows:




The higher the rate, the shorter the transmission distance.

If the distance exceeds the above limit, fiber amplifiers such as EDFA (Erbium Doped Fiber Amplifier, Erbium-doped fiber amplifier) ​​can be used to amplify weak optical signals to make them transmit farther; or use coherent optical modules for transmission. Of course neither is cheap and requires additional cost.

With the advent of the 5G era and the popularity of the Internet of Things, the information generated is explosively growing, which puts forward higher transmission performance requirements for the physical layer of the entire communication system.

As an important component, the optical module will continue to contribute to the development of communication.