The wavelength of an SFP (Small Form-factor Pluggable) module can vary depending on the specific type and application. SFP modules are available with different wavelengths to accommodate various fiber types and transmission requirements. Here are some common wavelengths for SFP modules:

1. 850nm: This wavelength is commonly used for multimode fiber in short-distance transmissions, such as within a data center. It is often associated with 1 Gbps and 10 Gbps Ethernet over multimode fiber.

2. 1310nm: SFP modules operating at 1310nm are used for both multimode and single-mode fiber. They are suitable for short to medium-distance transmissions and are commonly used in applications like 1 Gbps and 10 Gbps Ethernet.

3. 1550nm: This wavelength is often associated with SFP modules designed for single-mode fiber and longer-distance transmissions. It is commonly used in applications such as 1 Gbps, 10 Gbps, and 100 Gbps Ethernet for long-haul connections.

4. DWDM (Dense Wavelength Division Multiplexing): In some cases, SFP modules are designed for specific wavelengths within the DWDM spectrum, allowing for high-density wavelength multiplexing over a single fiber pair.

It's important to note that the choice of wavelength depends on factors such as the type of fiber optic cable being used, the transmission distance, and the specific requirements of the network. When selecting SFP modules, it's crucial to ensure compatibility with the network infrastructure and other connected devices.