Introduction:

The rise of big data, blockchain, cloud computing, Internet of Things, artificial intelligence, and 5G has led to a rapid increase in data traffic.  Data centers and optical interconnections for mobile communications have become research hotspots in the optical communication industry. In optical communication systems, optical modules play a very important role.  This article will introduce what optical modules are, common types of optical modules, and future development directions.

What is a light module?

Before understanding the optical module, let's briefly introduce optical communication

Brief Introduction to Optical Communication

Optical communication is a technology that uses light to transmit information to the other party. The computers and mobile phones around us transmit information through electrical signals "0 and 1". Optical communication consists of a "transmitter" that converts electrical signals into optical signals, a "receiver" that converts optical signals into electrical signals, and a "fiber optic" circuit that transmits light. Because optical signals are completely different from electrical signals, optical communication has advantages over electrical communication such as long transmission distance, economic energy conservation, one-time transmission of large amounts of information, and fast communication speed.  The "transmitter" and "receiver" mentioned above are the protagonists today - optical modules.

The concept of optical module

Optical transceivers are core components in optical communication, capable of completing the optical-to-electrical/electrical-to-optical conversion process of optical signals.  They consist of optoelectronic devices, functional circuits, and optical interfaces, among which the optoelectronic devices include both receiving and transmitting parts. Simply put, the receiving part is responsible for converting optical signals into electrical signals, while the transmitting part converts electrical signals into optical signals.

Working principle and classification of optical modules

Working principle of optical module

As mentioned above, optical modules are mainly divided into two parts, and their working principles are as follows:

Transmitting part: Inputting a certain bit rate of electrical signals, after processing by the internal drive chip, drives the semiconductor laser (LD) or light-emitting diode (LED) to emit modulated optical signals at the corresponding rate.  It has an internal optical power automatic control circuit to maintain the stability of the output optical signal power.

Receiving part: After being input into the module at a certain bit rate, the optical signal is converted into an electrical signal by an optical detection diode, and after passing through a preamplifier, the electrical signal at the corresponding bit rate is output.

Classification of optical modules

At present, optical modules are mainly classified according to their packaging, specifically as follows

XFP (10 Gigabit Small Form Factor Pluggable) is a hot-swappable, protocol-independent optical transceiver used for 10G bps Ethernet, SONET/SDH, and Fibre Channel.

2. Small form-factor pluggable transceiver (SFP) is currently the most widely used.

3. The GigacBiDi series of single-fiber bidirectional optical modules uses WDM technology to transmit bidirectional information signals over a single optical fiber (point-to-point transmission. Especially when there is a shortage of optical fiber resources, one optical fiber is required to transmit bidirectional signals). GigacBiDi includes SFP single-fiber bidirectional (BiDi), GBIC single-fiber bidirectional (BiDi), SFP+ single-fiber bidirectional (BiDi), XFP single-fiber bidirectional (BiDi), SFF single-fiber bidirectional (BiDi), and so on.

4. RJ45 electrical port small pluggable module, also known as electrical module or electrical port module.

5. SFF is divided into 2x5, 2x10, etc. according to its pins

6. Gigabit Ethernet Interface Converter (GBIC) Module

7. Passive Optical Network PON (A-PON, G-PON, GE-PON) Optical Modules

8.40Gbs high-speed optical module.

9. SDH transmission module (OC3, OC12, OC48)

10. Storage modules, such as 4G, 8G, etc. [2]

Application of optical modules

In enterprise network deployment and data center construction, optical modules and switches are inseparable. As mentioned above, among many optical modules, SFP+ optical modules are one of the most widely used optical modules.  When used with switches, different connection methods can be used to achieve different network requirements. Here are some practical application scenarios of SFP+ optical modules and switches.

Solution 1: connection between 10G SFP+ 10G optical module and switch

Insert four 10G SFP+ optical modules into the 10-Gbps SFP+ ports of one switch, insert a 40G QSFP+ optical module into the 40-Gbps QSFP+ port of another switch, and finally connect them with a branch fiber jumper in the middle.

This connection method mainly realizes the expansion of the network from 10G to 40G, which can quickly and easily meet the network upgrade requirements of data centers.

Scheme 2: Connection between BIDI SFP+ 10Gbps single-fiber bidirectional optical module and switch

Insert the optical modules into the SFP+ ports of the two switches, and then connect the optical modules on the two switches using LC fiber jumper cables that correspond to the optical module connection ports.

This connection method effectively implements the simplest and most economical data connection, and can be applied to data centers, enterprise cabling, and Ethernet connections for telecommunications operations and transmission.

Solution 3: connection between CWDM SFP+ 10G optical module and switch

This connection method uses relay boxes, optical transceivers, CWDM coarse wavelength division multiplexers, and other components to connect optical modules to switches, enabling the conversion of RJ45 electrical ports on 10G 10-gigabit Ethernet switches to CWDM wavelengths required by CWDM coarse wavelength division multiplexers.

Solution 4: Connection between DWDM SFP+ 10G optical module and switch

Insert the optical module into the SFP+ port of the switch, and then connect it to the DWDM dense wavelength division multiplexer with armored fiber jumper.

This connection method realizes the protection of optical signals during long-distance transmission, which can minimize the loss of optical waves and is suitable for long-distance optical signal transmission.

Conclusion:

Optical modules can be said to be the backbone of high bandwidth, high density, and low energy consumption data communication fields. In the next few years, with the advent of the 5G era, the concept of the meta universe continues to mature, including Google, Microsoft, Amazon, Facebook, Ali, Tencent, Baidu and other Internet companies in the world continue to build new data centers to deal with the challenge of data volume explosion, and the growth of the data market will be very significant. The demand for optical modules/devices in the data communication market is much greater than in other sub industries.  Data center switches with a capacity of over 100G and supporting high-speed optical modules will usher in a development boom, and the market structure will gradually increase.  Let's wait and see!