Multimode optical module:
Fibers that can propagate hundreds to thousands of modes are called multimode (MM) fibers. According to the radial distribution of refractive index in the core and cladding, it can be divided into step multimode fiber and graded multimode fiber. Almost all multimode fibers are 50/125μm or 62.5/125μm in size, and the bandwidth (the amount of information transmitted by the fiber) is usually 200MHz to 2GHz. Multi-mode optical transceivers can transmit up to 5 kilometers through multi-mode optical fibers. Use light-emitting diodes or lasers as light sources.
Single-mode optical module:
Fibers that can only propagate one mode are called single-mode fibers. The refractive index profile of standard single-mode (SM) fiber is similar to that of step-type fiber, except that the core diameter is much smaller than that of multi-mode fiber.
The size of single-mode fiber is 9-10/125μm, and compared with multi-mode fiber, it has unlimited bandwidth and lower loss characteristics. The single-mode optical transceiver is mostly used for long-distance transmission, sometimes up to 150 to 200 kilometers. Use LD or LED with narrow spectral line as the light source.
Differences and connections:
Single-mode equipment usually runs on single-mode fiber or multi-mode fiber, while multi-mode equipment is limited to running on multi-mode fiber.