What is the difference between SFP and SFP+ optical modules?
First of all, we need to understand the various parameters of the optical module, among which there are three main types (center wavelength, transmission distance, transmission rate), and the main differences between optical modules are also reflected in these points.
1. Central wavelength The unit of central wavelength is nanometer (nm), currently there are three main types:
1) 850nm (MM, multi-mode, low cost but short transmission distance, generally only 500m);
2) 1310nm (SM, single mode, large loss but small dispersion during transmission, generally used for transmission within 40km);
3) 1550nm (SM, single mode, small loss but large dispersion in the transmission process, generally used for long-distance transmission over 40km, and can directly transmit 120km without a relay).
2. Transmission distance Transmission distance refers to the distance that optical signals can be directly transmitted without relay amplification, and the unit is kilometers (also called kilometers, km). Optical modules generally have the following specifications: multi-mode 550m, single-mode 15km, 40km, 80km and 120km and so on.
3. Transmission rate The transmission rate refers to the number of bits of data transmitted per second (bit), and the unit is bps. The transmission rate is as low as 100M and as high as 100Gbps. There are four commonly used rates of 155Mbps, 1.25Gbps, 2.5Gbps and 10Gbps. The transmission rate is generally downward. In addition, in the optical fiber storage system (SAN), the optical module has three rates of 2Gbps, 4Gbps and 8Gbps.
After understanding the above three optical module parameters, do you have a preliminary understanding of the optical module? If you want to know more, let’s take a look at other parameters of the optical module!
1. Loss and dispersion: Both of them mainly affect the transmission distance of the optical module. Generally, the link loss of 1310nm optical module is calculated at 0.35dBm/km, the link loss of 1550nm optical module is calculated at 0.20dBm/km, and the calculation of dispersion value It is very complicated and generally only for reference;
2. Loss and dispersion: These two parameters are mainly used to define the transmission distance of the product. The optical transmission power and receiving sensitivity of optical modules with different wavelengths, transmission rates and transmission distances will be different;
3. Lasers Category: At present, FP and DFB are the most commonly used lasers. The semiconductor materials and resonant cavity structures of the two are different. DFB lasers are expensive and are mostly used for optical modules with transmission distances greater than 40km; FP lasers are cheap and generally used For optical modules with a transmission distance within 40km;
4. Optical fiber interface: SFP optical modules are all LC interfaces, GBIC optical modules are all SC interfaces, and other interfaces include FC and ST;
5. The service life of the optical module: the international unified standard, 7×24 hours of uninterrupted work for 50,000 hours (equivalent to 5 years);
6. Environment: Working temperature: 0~+70℃; Storage temperature: -45~+80℃; Working voltage: 3.3V; Working level: TTL.
Then, according to the above introduction to the optical module parameters, let’s understand the differences between the SFP optical module and the SFP+ optical module.
1. The definition of SFP SFP (Small form-factor pluggable) means small form-factor pluggable. It is a pluggable module that can support Gigabit Ethernet, SONET, Fiber Channel and other communication standards and plug into the SFP port of the switch. The SFP specification is based on IEEE802.3 and SFF-8472, which are capable of supporting speeds up to 4.25 Gbps. Due to its smaller size, SFP replaces the previously common Gigabit Interface Converter (GBIC), so it is also called mini GBIC SFP. By selecting SFP modules with different wavelengths and ports, the same electrical port on the switch can be connected to optical fibers with different connectors and different wavelengths.
2. The definition of SFP+ Since SFP only supports a transmission rate of 4.25 Gbps, it cannot meet people’s requirements for higher and higher network speeds. SFP+ was born under such a background. The maximum transmission rate of SFP+ can reach 16 Gbps. In fact, SFP+ is an enhanced version of SFP. The SFP+ specification is based on SFF-8431. In most applications today, SFP+ modules typically support 8 Gbit/s Fiber Channel. With its advantages of small size and convenient use, the SFP+ module has replaced the XENPAK and XFP modules that were widely used in the early 10 Gigabit Ethernet, and has become the most popular optical module in the 10 Gigabit Ethernet.
After analyzing the above definitions of SFP and SFP+, it can be concluded that the main difference between SFP and SFP+ is the transmission rate. And because the data rate is different, the application and transmission distance are also different. After understanding the above optical module knowledge, I believe that everyone’s understanding of optical modules has been greatly improved.
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