1. What are single-mode optical modules and multimode optical modules?

Single-mode (SM) optical modules have limited use and are suitable for long-distance data transmission.  Multi-mode (MM) optical modules can transmit multiple modes of light and are suitable for short-distance transmission. Single-mode and multi-mode in optical modules actually refer to the types of optical fibers connected to the optical modules.

2. Difference between single-mode optical module and multimode optical module

(1) Different wavelengths

The working wavelength of multimode optical modules is generally 850nm, while that of single-mode optical modules is generally 1310nm and 1550nm.

(2) Different transmission distances

Single-mode optical modules are commonly used for long-distance transmission, with transmission distances up to 150 to 200km. Multimode optical modules are mostly used for short-distance transmission, with transmission distances up to 2km.

(3) Different types of optical fibers

According to the transmission mode of optical modules in optical fibers, optical fibers can be divided into single-mode optical fibers and multimode optical fibers. The fiber diameter of multimode optical fibers (MMF) is generally 50/125μm or 62.5/125μm, while the fiber diameter of single-mode optical fibers (SMF) is 9/125μm.

(4) Different light sources

The light source of a single-mode optical module is an LD or a LED with a narrow spectral line, while the light source of a multimode optical module is a light-emitting diode or a laser.

(5) Different application scope

Single-mode optical modules are mostly used in lines with relatively high transmission rates and relatively long distances, such as metropolitan area network construction. Multimode optical modules are mostly used for short-distance transmission, and transmission with many network nodes and connectors is also very suitable for the application of multimode optical modules. In addition, multimode devices can only operate effectively on multimode optical fibers, while single-mode devices can operate on both single-mode and multimode optical fibers, but single-mode devices cannot guarantee the effect on multimode optical fibers. (6) Different prices

Although single-mode fiber is cheaper than multimode fiber, single-mode optical modules are much higher than multimode optical modules.

3. Precautions for using single-mode optical modules and multimode optical modules

When using a single-mode optical module, it is necessary to ensure that the actual received optical power is less than the overload optical power.  Therefore, it is necessary to measure the optical power and selectively use an optical attenuator in conjunction with the optical module.

When using a single-mode optical module, there should be a margin of receiving power.

(3) Multi-mode optical modules can only transmit signals of one wavelength and cannot be used in conjunction with multiplexers

(4) Multimode optical modules are limited to operating on multimode optical fibers