Difference between sfp and sfp+ modules

Many people are unclear about the difference between SFP and SFP+, which sometimes causes unnecessary complications. The development of 10G modules has gone through several stages, including 300Pin, XENPAK, X2, and XFP, before finally achieving the transmission of 10G signals using the same form factor as SFP, known as SFP+. SFP, with its advantages of small size and low cost, meets the high-density requirements for optical modules in devices. It became the mainstream in the 10G market by replacing XFP from the year 2002, and by 2010.
SFP (Small Form-factor Pluggable) and SFP+ (Small Form-factor Pluggable Plus) modules are used for networking purposes and are interchangeable with each other. However, there are some key differences between them:

1. Speed:

SFP modules support data rates up to 1 Gbps, while SFP+ modules support data rates up to 10 Gbps.

2. Distance:

 SFP modules are generally used for short distances up to 550 meters, while SFP+ modules are used for longer distances up to 10 kilometers.

3. Power consumption:

SFP modules consume less power than SFP+ modules, making them suitable for low-power devices.

4. Cost:

SFP modules are less expensive than SFP+ modules, making them a more cost-effective option for lower speed networks.

5. Size:

SFP+ modules are smaller than SFP modules, with dimensions of 10mm x 13mm x 56mm, while SFP modules have dimensions of 10mm x 13mm x 59mm.

6. Compatibility:

SFP+ modules are not compatible with the interface of SFP modules, but compatibility can be achieved through adapters. On the other hand, SFP modules can be made compatible with SFP+ modules through adapters as well.
 
SFP modules are suitable for lower speed and shorter distance networks, while SFP+ modules are suitable for higher speed and longer distance networks.
 
In summary, the main differences between SFP+ and SFP modules are in terms of transmission rate, size, power consumption, Compatibility,and transmission distance. Users should choose the appropriate optical module based on their specific requirements.
 

Expand knowledge:

SFP and SFP+ optical modules have different parameters and differences.
First, let's understand the various parameters of optical modules, with the most important ones being three: center wavelength, transmission distance, and transmission rate. The main differences between optical modules are also reflected in these aspects.

1. Center Wavelength:

The unit of center wavelength is nanometers (nm), and there are mainly three types:
- 850nm (MM, multimode, low cost but short transmission distance, usually limited to 500m)
- 1310nm (SM, single mode, higher loss but smaller dispersion, typically used for transmissions within 40km)
- 1550nm (SM, single mode, lower loss but larger dispersion, generally used for long-distance transmissions beyond 40km, can directly transmit up to 120km without relay)

2. Transmission Distance:

The transmission distance refers to the distance at which the optical signal can be transmitted without the need for relay amplification, measured in kilometers (km). The common specifications of optical modules include multimode 550m, single mode 15km, 40km, 80km, 120km, etc.

3. Transmission Rate:

The transmission rate refers to the number of bits transmitted per second, measured in bits per second (bps). The transmission rates can range from hundreds of megabits to 100Gbps. The commonly used rates are 155Mbps, 1.25Gbps, 2.5Gbps, and 10Gbps. In addition, in fiber channel storage area networks (SANs), optical modules also have rates of 2Gbps, 4Gbps, and 8Gbps.
Having understood the above three main parameters of optical modules, you should have a preliminary understanding of them. To further enhance your knowledge, let's take a look at other parameters of optical modules:

1. Loss and Dispersion:

Both loss and dispersion mainly affect the transmission distance of optical modules. Generally, the loss of 1310nm optical modules is calculated at 0.35dBm/km, while the loss of 1550nm optical modules is calculated at 0.20dBm/km. The calculation of dispersion value is complex and usually serves as a reference only.

2. Laser Diode Category:

The most commonly used types are FP (Fabry-Perot) and DFB (Distributed Feedback) laser diodes. Their semiconductor materials and resonant cavity structures differ. DFB laser diodes are more expensive and are used in optical modules for transmission distances greater than 40km, while FP laser diodes are cheaper and are generally used for transmission distances within 40km.

3. Fiber Interfaces:

SFP optical modules have LC interfaces, while GBIC optical modules have SC interfaces. Other interfaces include FC and ST.

4. Lifespan of Optical Modules:

The international standard is continuous operation for 50,000 hours (equivalent to 5 years).

5. Environment:

Working Temperature: 0~+70°C; Storage Temperature: -45~+80°C; Working Voltage: 3.3V; Logic Level: TTL.
Now, based on the introduction of the parameters above, let's understand the differences between SFP optical modules and SFP+ optical modules.

1. SFP Definition:

SFP (Small Form-Factor Pluggable) stands for a small pluggable module that supports Gigabit Ethernet, SONET, Fiber Channel, and other communication standards. It can be inserted into the SFP port of a switch. SFP specifications are based on IEEE 802.3 and SFF-8472, supporting speeds up to 4.25 Gbps. Due to its smaller size, SFP replaces the previously common Gigabit Interface Converter (GBIC) and is also known as Mini-GBIC SFP. By selecting SFP modules with different wavelengths and ports, the same electrical port on a switch can be connected to various connectors and different-wavelength fibers.

2. SFP+ Definition:

As SFP only supports a transmission rate of up to 4.25 Gbps, it cannot meet the increasing demand for high internet speeds. Therefore, SFP+ was created as an enhanced version of SFP. The maximum transmission rate of SFP+ can reach 16 Gbps. In most applications today, SFP+ modules typically support 8 Gbit/s Fiber Channel. Due to their small size and convenience, SFP+ modules have replaced the earlier XENPAK and XFP modules, becoming the most popular optical modules for 10 Gigabit Ethernet.
Based on the analysis of the definitions of SFP and SFP+, the main difference between them is the transmission rate. Moreover, due to the different data rates, their applications and transmission distances also differ.