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Optical module is one of the important parts of industrial switch. although many people know that there is optical module, they do not know much about it. For example, there is not much difference between SFP+ optical module and SFP optical module in appearance, but the function is very different. So what are the parameters of the optical module? What is the difference between SFP and SFP+ optical modules? The following Huashu Communications will give you a detailed introduction!

Description of the parameters of the optical module

1. Central wavelength

The unit of central wavelength is nanometer (nm). At present, there are mainly three kinds:

1) 850nm (MM, multimode, low cost but short transmission distance, generally only 500m)

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

3) 1550nm (SM, single mode, with low loss but large dispersion in the transmission process, is generally used for long-distance transmission above 40km, and can transmit 120km directly without relay at most).

2. Transmission distance

Transmission distance refers to the distance that optical signals can be transmitted directly without relay amplification, in kilometers (also known as kilometers, km). Optical modules generally have the following specifications: multimode 550m, single-mode 15km, 40km, 80km and 120km and so on.

3. Transmission rate

The transmission rate refers to the number of bits per second (bit) of data transmitted, in bps. The transmission rate is as low as 100 megabits and as high as 100Gbps, and the commonly used rates are 155Mbps, 1.25Gbps, 2.5Gbps and 10Gbps. The transmission rate is generally downward. In addition, in the optical storage system (SAN), the optical module also has three rates: 2Gbps, 4Gbps and 8Gbps.

4. Loss and dispersion

Both of them mainly affect the transmission distance of optical modules. in general, 1310nm optical module uses 0.35dBm/km to calculate link loss, 1550nm optical module uses 0.20dBm/km to calculate link loss, the calculation of dispersion value is very complex, generally only for reference.

5. Loss and dispersion

These two parameters are mainly used to define the transmission distance of the product. The optical transmission power and reception sensitivity of optical modules with different wavelengths, transmission rates and transmission distances will be different.

6. Laser category

At present, the most commonly used lasers are FP and DFB lasers, whose semiconductor materials and cavity structures are different. DFB lasers are expensive and are mostly used for optical modules whose transmission distance is larger than 40km, while FP lasers are cheap and are generally used for optical modules with transmission distances within 40km.

7. Optical fiber interface

SFP optical modules are all LC interfaces, GBIC optical modules are SC interfaces, and other interfaces are FC and ST.

8. Service life of optical module

International uniform standard, 7 × 24 hours of uninterrupted work 50,000 hours (equivalent to 5 years)

9. Environment

The working temperature is 70 ℃, the storage temperature is-45 ℃, the working voltage is 3.3 V, and the working level is TTL.

2. The difference between SFP optical module and SFP+ optical module

SFP (Small form-factor pluggable) means small, 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 4.25Gbps. Because of its small size, the SFP replaces the previously common gigabit interface converter (GBIC), so it is also known as the mini GBIC SFP. By selecting SFP modules with different wavelengths and ports, the same electric port on the switch can be connected to different interfaces and different wavelengths of optical fiber.

Because SFP only supports the transmission rate of 4.25Gbps, which can not meet the requirements of higher and higher network speed, SFP+ was born under this background. The highest transmission rate of SFP+ can reach 16Gbps. 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 8Gbit/s fibre Channel. With the advantages of small size and easy to use, SFP+ module has replaced the XENPAK and XFP modules which were widely used in early 10 Gigabit Ethernet, and become the most popular optical module in 10 Gigabit Ethernet.

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