What is Optical Module?

Ⅰ. What is an optical module?

A. What's the definition of the optical module?

A photoelectric and electro-optical conversion optical module is an optoelectronic device. The optical module's transmitting end converts the electrical signal to an optical signal, while the receiving end converts the optical signal back to an electrical signal. Optoelectronic devices, functional circuitry, and optical interfaces make up this system. There are two parts to the optoelectronic device: sending and receiving. SFP, SFP+, SFF, Gigabit Ethernet Interface Converter (GBIC), and other optical modules are categorized according to their packaging type.

B. What does the optical module consist of?

Light-emitting components (such as lasers), light-receiving components (such as detectors), driving circuits, and photoelectric interfaces are common components of optical modules. The diagram below depicts the structure.

C. What's the classification of optical modules?

According to the functions

Optical receiving, optical transmitting, optical transceiver, and optical forwarding modules are only a few examples.

The integrated optical transceiver module's main function is to perform photoelectric/electro-optical conversion, which includes functions such as optical power control, modulation and transmission, signal detection, IV conversion, and limiting amplification judgment regeneration, as well as anti-counterfeiting information query, TX-disable, and other functions. SFP, SFF, SFP+, GBIC, XFP, 1x9, and so on.

The optical forwarding module includes several signal processing tasks in addition to photoelectric conversion, such as MUX/DEMUX, CDR, function control, energy collection, and monitoring. 200/300pin, XENPAK, and X2/XPAK are examples of common optical forwarding modules.

The "optical module" or "optical module" refers to the integrated optical transceiver module, which is the English term for the "transceiver." It's a crucial part of the optical fiber communication infrastructure.

According to the parameters

Pluggability: hot-swappable and non-hot-swappable

Package form: SFP, GBIC, XFP, Xenpak, X2, 1X9, SFF, 200/3000pin, XPAK.

Transmission rate: The transmission rate is measured in megabits per second (MB/s) or gigabits per second (GB/s). The following main rates are covered by optical module products: low rate, 100M, Gigabit, 2.5G, 4.25G, 4.9G, 6G, 8G, 10G, and 40G.

According to the package

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

2. SFP (small pluggable receiving and light-emitting module), which is the most extensively utilized at the moment.

3. The GigacBiDi series single-fiber bidirectional optical module use WDM technology to achieve two-way information transfer (point-to-point transmission) over fiber. The shortage of fiber resources, in particular, necessitates the use of only one fiber to transport two-way signals). 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 SFP+ single fiber bidirectional (BiDi) are all examples of GigacBiDi.

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

5. SFF is divided into 2x5, 2x10, and so on, based on the number of pins.

6. Gigabit Ethernet interface converter (GBIC) module

7. Passive optical network PON (A-PON, G-PON, GE-PON) optical module

8.40Gbs high-speed optical module.

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

10. Storage modules, such as 4G, 8G, etc.

D. What's the function of the optical module?

Optical modules carry out the transmission and reception of data in optical communication:

1. The optical module completes the electrical/optical conversion at the transmitting end.

2. Light travels through the optical fiber.

3. The optical module performs optical/electrical conversion at the receiving end.

The Function of Optical Module

E. Where can the optical module be used?

The optical module is mostly employed in the field of data communication, and its function is to realize photoelectric signal mutual conversion. Data traffic has increased rapidly as a result of the rise of big data, blockchain, cloud computing, the Internet of Things, artificial intelligence, and 5G, and optical interconnection of data centers and mobile communications has emerged as a research hotspot in the optical communications industry. ETU-LINK will then go over the many fields in which the optical module can be used.

1. Data Center

The data center's host room houses a huge number of network switches, server clusters, and other equipment. They are the data convergence center of the information network system, as well as the heart of integrated wiring and information network equipment. To enable Data intercommunication, ETU-LINK optical modules (direct-connect copper cables, active optical cables), optical fiber jumpers, and other transmission carriers must be used in the connections between servers, switches, and servers and switches. 

With the growing demand for data transfer, IDC computer rooms can help small and medium-sized businesses compete more effectively. Different types of network equipment and transmission carriers (active optical cables, direct-connected copper cables, optical modules, optical fiber jumpers) have emerged as a result of the diversification of data center connecting scenarios and the individualization of client needs. Similarly, when it comes to accessories, you must choose based on the application circumstance.

2. Mobile communication base station

Optical modules are also required by operators' mobile communication base stations in order to link devices. RRU and BBU devices are installed in the base stations. We need to connect the links between these two devices in the application, which necessitates the use of our optical modules. The equipment used to connect BBUs and RRUs in 4G networks with fiber jumpers is primarily 1.25G optical modules, 2.5G optical modules, 6G optical modules, and 10G optical modules.

3. Passive WDM System

Metro area networks, backbone networks, and wide area networks all use passive wavelength division systems. CWDM and DWDM optical modules are widely utilized. The CWDM optical module is one of them. It uses CWDM technology to combine optical signals of different wavelengths via an external wavelength division multiplexer and send them over a single optical fiber, saving optical fiber resources. At the same time, the receiving end must deconstruct the complicated optical signal using a wavelength division multiplexer.

The channel spacing in passive wavelength division multiplexing (CWDM) is 20nm, the working wavelength is 1270-1610nm, and the maximum distance is 40 kilometers. The back wave (1470-1610nm) is used in CWDM optical modules, and the transmission distance is 10KM or 20KM. Optical CWDM The module makes use of the entire band (1270-1610nm).

In most CWDM systems, CWDM optical modules are employed. They are less expensive and more extensively used than DWDM optical modules. The CWDM optical module is plugged into the switch in a CWDM system, and the CWDM optical module is jumpered to the CWDM demultiplexer or OADM optical add/drop multiplexer.

4. SAN/NAS storage network

The SAN/NAS storage network's primary job is to store data. SAN storage networks are primarily made up of servers, Fibre Channel switches, storage devices, and transmission carriers (optical modules, fiber jumpers); NAS storage networks are primarily made up of NAS storage, switches, terminal equipment (computer), and transmission carriers (optical modules, fiber jumpers) (optical module, optical fiber jumper). The SAN network uses Fibre Channel optical modules and must support the FC Fibre Channel protocol, whereas the optical modules in the NAS storage network must merely conform with the Ethernet standard.

(1). The schematic diagram of the NAS storage network is shown below:

2. The schematic diagram of the SAN storage network is shown below:

5. 5G bearer network

The optical module sector has been given a fresh lease of life with the arrival of the 5G era. 5G bearer networks are divided into four layers: metro access, metro convergence, metro core layer/intra-provincial trunk lines, and metro core layer/intra-provincial trunk lines, and they enable the fronthaul and transmission of 5G services. Each layer of equipment relies on the optical module to achieve connections in the backhaul function.

The 25G SFP28 (eCPRI/CPRI) optical modules used in the 5G fronthaul network include dual-fiber bidirectional, single-fiber BiDi, 25G WDM (including Tunable wavelength-tunable) modules, and other options.

Backhaul in 5G is primarily comprised of 25G, 50G, 100G, 200G, and 400G optical modules that support several interface protocols such as CPRI, eCPRI, Ethernet, and OTN, as well as modulation formats such as NRZ, PAM4, and DMT.

Ⅱ. What are the development trend and technical routes of optical modules?

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

Ⅲ. What is the package of optical modules?

The optical module's most essential feature is its packaging form.

The packaging form standard establishes the compatibility and interconnection of optical modules made by diverse manufacturers.

The bandwidth of devices and chips has gradually increased with the advent of optoelectronic technologies. The bandwidth of devices and circuits has risen, and optical modules have achieved better rate transmission and lower size packages as a result of the development of photonic integration technology.

The evolution of optical module packaging is depicted in the diagram below.

Ⅳ. How to increase the transmission rate of optical modules?

Various 5G applications are made possible by high-speed data transfer.

The transmission rate is measured in megabits per second (MB/s) or gigabits per second (GB/s). From the early 155 Mb/s, optical modules have gradually increased: 622 Mbps, 1.25 Gigabits per second, 2.5 Gigabits per second, 10 Gigabits per second, 25, 50, 100 Gigabits per second, 200 Gigabits per second, 400 Gigabits per second, 800 Gigabits per second

The following three solutions are commonly used to get a greater rate:

1. Increase the light source baud rate

Bottleneck: the performance of III-V semiconductor lasers. The current 50G light source solutions are all externally modulated EML

2. Increase the number of channels

Difficulties: design and packaging of size, power consumption, heat dissipation, etc. Increase the cost of light resources for customers

3. High-order modulation

There are two main types: PAM4 and coherent modulation. PAM4 is currently the most commonly used 400G optical module, but the chip cost is correspondingly increased.

Ⅴ. What does DR, LR, ER in the transmission distance of an optical module mean?

Faster and farther has always been the unrelenting desire of communication people in the field of optical communication.

In the early stages, the optical module's transmission distances primarily include SR (100 m), LR (10 km), ER (40 km), and ZR (80 km).

Two transmission distances, DR (500 m) and FR (2 km), have been developed for the construction of data center networks in order to have more cost-effective wiring.

The following are typical optical module transmission distances:

The shorter the transmission distance, the higher the rate.

If the distance is greater than the aforementioned limit, fiber amplifiers, such as the EDFA (Erbium-Doped Fiber Amplifier), can be used to amplify weak optical signals and send them further, or coherent optical modules can be employed. Both, of course, are not inexpensive and necessitate further expenditures.

With the arrival of the 5G era and the widespread use of the Internet of Things, the amount of data generated has increased dramatically, necessitating higher transmission performance requirements on the physical layer of the entire communication system.

It will continue to contribute to the advancement of communications as a vital component of the optical module.