First of all, we need to understand the various parameters of optical modules, of which there are three main types (central wavelength, transmission distance, transmission rate), and the main differences between optical modules are also reflected in these points.

1.Center wavelength

The unit of the center wavelength is nanometer (nm), currently there are three main types:

1) 850nm (MM, multi-mode, low cost but short transmission distance, generally only 500m transmission);

2) 1310nm (SM, single mode, large loss but small dispersion during transmission, generally used for transmission within 40km);

3) 1550nm (SM, single-mode, low loss but large dispersion during transmission, generally used for long-distance transmission above 40km, and the farthest can be directly transmitted without relay 120km).

2. Transmission distance

Transmission distance refers to the distance that optical signals can be transmitted directly without relay amplification. 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, etc. Wait.

3.Transmission rate

The transmission rate refers to the number of bits (bits) of data transmitted per second, in bps. The transmission rate is as low as 100M and as high as 100Gbps. There are four commonly used rates: 155Mbps, 1.25Gbps, 2.5Gbps and 10Gbps. The transmission rate is generally downward. In addition, there are 3 types of speeds of 2Gbps, 4Gbps and 8Gbps for optical modules in optical storage systems (SAN).

After understanding the above three optical module parameters, do you have a preliminary understanding of the optical module? If you want a further understanding, let’s take a look at the other parameters of the optical module!

1.Loss and dispersion: Both mainly affect the transmission distance of the optical module. Generally, the link loss is calculated at 0.35dBm/km for the 1310nm optical module, and the link loss is calculated at 0.20dBm/km for the 1550nm optical module, and the dispersion value is calculated Very complicated, generally for reference only;

2.Loss and chromatic dispersion: These two parameters are mainly used to define the transmission distance of the product, the optical emission of optical modules with different wavelengths, transmission rates and transmission distances Power and receiving sensitivity will be different;

3.Laser category: At present, the most commonly used lasers are FP and DFB. The semiconductor materials and resonator structure of the two are different. DFB lasers are expensive and are mostly used for optical modules with transmission distances greater than 40km; while FP lasers are cheap , Generally used for optical modules with a transmission distance of less than 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 uniform 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.

So based on the above introduction to the optical module parameters, let’s understand the difference between SFP optical module and SFP+ optical module.

1.Definition of SFP

SFP (Small form-factor pluggable) means small form-factor pluggable. It is a pluggable module that can support Gigabit Ethernet, SONET, Fibre 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 can support 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 different connectors and optical fibers of different wavelengths.

2.Definition of SFP+

Because SFP only supports a transmission rate of 4.25 Gbps, which cannot meet people’s increasing requirements for network speeds, SFP+ was born under this 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 usually support 8 Gbit/s Fibre Channel.The SFP+ module has replaced the XENPAK and XFP modules that were more commonly used in the early 10 Gigabit Ethernet due to its small size and convenient use, and has become the most popular optical module in the 10 Gigabit Ethernet.

After analyzing the above definition of SFP and SFP+, it can be concluded that the main difference between SFP and SFP+ is the transmission rate. And because of different data rates, applications and transmission distances are also different.