What is the packaging of optical modules?
For those who are new to the optical module, the optical module is very maddening because of its extremely complicated package name and dazzling parameters.
Packaging can be simply understood as a standard model. It is the most important way to distinguish optical modules.
The reason why there are so many different packaging standards for optical modules is mainly that the development speed of optical fiber communication technology is too fast.
The rate of optical modules continues to increase, and the volume continues to shrink, so that every few years, new packaging standards will be released. It is often difficult to be compatible with new and old packaging standards.
In addition, the diversity of application scenarios of optical modules is also a reason for the increase in packaging standards. Different transmission distances, bandwidth requirements, and places of use correspond to different types of optical fibers and optical modules.
I briefly listed the classification of optical modules including packaging, as shown in the following table:
Before explaining packaging and classification, we first introduce the standardization organization of optical communication. Because these packages are determined by the standardization organization.
There are currently several organizations that standardize optical communications worldwide, such as the IEEE (Institute of Electrical and Electronics Engineers), ITU-T (International Telecommunication Union), MSA (Multi-Source Agreement), and OIF (Optical Interconnect), which are familiar to everyone. Forum), CCSA (China Communications Standards Association), etc.
The most used in the industry are IEEE and MSA.
MSA may not be familiar to everyone. Its English name is Multi-Source Agreement. It is a multi-vendor specification. Compared with IEEE, it is a non-governmental organization form, which can be understood as the behavior of enterprise alliances in the industry.
Okay, let's start introducing packaging.
First of all, you can take a look at the following picture, which describes the appearance period of different packages and the corresponding working rate more accurately.
We don't care about the standards that are too old or very rare, mainly looking at common packages.
GBIC
GBIC is the Giga Bitrate Interface Converter.
Before 2000, GBIC was the most popular optical module package and the most widely used gigabit module form.
SFP
Because of the relatively large size of GBIC, later, SFP appeared and began to replace GBIC.
SFP stands for Small Form-factor Pluggable, which is a small hot-swappable optical module. Its small size is relative to GBIC packaging.
The volume of the SFP is reduced by half compared to the GBIC module, and more than double the number of ports can be configured on the same panel. In terms of function, the two are not much different, and both support hot-swapping. The maximum
bandwidth supported by SFP is 4Gbps.
XFP
XFP is 10-Gigabit Small Form-factor Plugable, which can be understood at a glance, it is 10G SFP.
XFP uses an XFI (10Gb serial interface) connected full-speed single-channel serial module, which can replace Xenpak and its derivatives.
SFP+
SFP+, like XFP, is a 10G optical module.
The size of SFP+ is the same as SFP, more compact than XFP (reduced by about 30%), and the power consumption is also smaller (reduced some signal control functions).
SFP28
The SFP with a rate of 25Gbps was mainly due to the fact that the price of 40G and 100G optical modules was too expensive at that time, so much a compromise transition solution was implemented.
QSFP/QSFP+/QSFP28/QSFP28-DD
Quad Small Form-factor Pluggable, four-channel SFP interface. Many mature key technologies in XFP are applied to this design.
According to the speed, QSFP can be divided into 4×10G QSFP+, 4×25G QSFP28, 8×25G QSFP28-DD optical modules, etc.
Take QSFP28 as an example, it is suitable for 4x25GE access ports. Using QSFP28 can directly upgrade from 25G to 100G without going through 40G, which greatly simplifies the wiring difficulty and reduces costs.
QSFP-DD, established in March 2016, DD refers to "Double Density". QSFP's 4 channels have been added to a row of channels to become 8 channels.
It is compatible with the QSFP solution, the original QSFP28 module can still be used, just insert another module. QSFP-DD has twice as many gold fingers as QSFP28.
Each channel of QSFP-DD adopts 25Gbps NRZ or 50Gbps PAM4 signal format. With PAM4, it can support up to 400Gbps.
CFP/CFP2/CFP4/CFP8
Centum gigabits Form Pluggable, dense wavelength division optical communication module. The transmission rate can reach 100-400Gbps.
CFP is designed on the basis of the SFP interface, the size is larger and supports 100Gbps data transmission. CFP can support a single 100G signal, one or more 40G signals.
The difference between CFP, CFP2, and CFP4 is volume. The volume of CFP2 is one-half of CFP, and CFP4 is one-fourth of CFP.
CFP8 is a package specifically proposed for 400G, and its size is equivalent to CFP2. Supports 25Gbps and 50Gbps channel rates, and achieves a 400Gbps module rate through 16x25G or 8x50 electrical interfaces.
OSFP
This is a bit confusing with the OSPF routing protocol we often say.
OSFP, Octal Small Form Factor Pluggable, "O" stands for "Octal", officially launched in November 2016.
It is designed to use 8 electrical channels to achieve 400GbE (8*56GbE, but the 56GbE signal is formed by 25G DML laser under PAM4 modulation), the size is slightly larger than QSFP-DD, higher wattage optical engine and transceiver The heat dissipation performance is slightly better.
The above are some common optical module packaging standards.
What is an optical module? What is the structure of the optical module?
With the continuous development of the optical communication industry and the continuous improvement of network users' requirements for network service quality, the optical fiber communication system has become closer to everyone's life.
Higher bandwidth and port density and lower energy consumption have become the constant pursuit of optical fiber communication systems. In the entire system, the optical module plays a very important role. Here is a brief introduction to the optical module.
First, what is an optical module? The optical module is called the optical transceiver module, which is the core device in optical communication and can complete the optical-electrical/electrical-optical conversion process of optical signals.
What is the structure of the optical module? The optical module is a collective name for various module categories. Although it looks small, its composition structure is not simple, including optical receiving module, optical sending module, optical transceiver module, and optical forwarding module.
The optical modules that we usually call today generally refer to integrated optical transceiver modules, such as QSFP8 optical modules. I will introduce you in detail in the following articles about the classification of optical modules.
The optical module works at the physical layer, which is the lowest layer in the OSI model. Its role is very simple to say, it is to achieve photoelectric conversion. Turn optical signals into electrical signals and electrical signals into optical signals.
Although it seems simple, the technical content of the implementation process is not low.
An optical module usually consists of a light-emitting device (TOSA, including a laser), a light-receiving device (ROSA, including a photodetector), a functional circuit, and an optical (electrical) interface.
At the transmitting end, the driver chip processes the original electrical signal and then drives the semiconductor laser (LD) or light-emitting diode (LED) to emit a modulated optical signal.
At the receiving end, after the optical signal comes in, it is converted into an electrical signal by the light detection diode, and the electrical signal is output after passing through the preamplifier.
The above are some brief introductions about optical modules. The following will introduce the package types of optical modules.
