Wavelength of optical modules in the computer room

Common optical module wavelengths are 850 nm, 1310 nm, and 1550 nm, with CWDM and DWDM modules covering broader ranges for high-capacity networks.

Standard Wavelengths

Optical modules operate at specific center wavelengths, which are the nominal wavelengths of light used for transmission. The most commonly used wavelengths in computer room networks are: 850 nm: Typically used for short-distance multimode fiber connections up to 500 meters, often with LED or VCSEL light sources. 1310 nm: Used for medium-distance multimode or single-mode fiber, covering distances from 500 meters to 20 km.

1550 nm: Preferred for long-distance single-mode fiber, generally for distances above 20 km, due to lower attenuation and reduced signal loss.

CWDM and DWDM Wavelengths

For high-capacity networks using Wavelength Division Multiplexing (WDM): CWDM (Coarse WDM): Wavelengths range from 1270 nm to 1610 nm, allowing multiple channels on a single fiber with wider spacing.

DWD

M (Dense WDM): Wavelengths range from 1525 nm to 1565 nm or 1570 nm to 1610 nm, enabling closely spaced channels for very high data throughput.

Fiber Type Considerations

Multimode fiber: Optimized for 850 nm and 1300 nm, suitable for short to medium distances in a computer room environment. Single-mode fiber: Optimized for 1310 nm and 1550 nm, ideal for longer runs and backbone connections.

Practical Implications

Choosing the correct wavelength ensures minimal attenuation, optimal signal integrity, and compatibility with the fiber type. For example, using 850 nm on single-mode fiber is inefficient due to higher loss, while 1550 nm on multimode fiber may not couple efficiently. In modern data centers, CWDM and DWDM modules are increasingly used to maximize fiber utilization and support high-speed links without laying additional fiber.

Selecting the appropriate optical module wavelength is therefore critical for network performance, distance coverage, and future scalability in computer room environments.