The difference between single mode fiber and multimode fiber
Fiber is a fiber made of glass or plastic that can be used as a light transmission medium, mainly used in the communication industry. Fiber has the advantages of wide bandwidth, long distance, anti-interference, security and reliability, light weight and durability. Fiber can be divided into single-mode fiber and multimode fiber according to the transmission mode. This article will introduce their differences and functions from the following aspects:
The main difference between single-mode fiber and multimode fiber is their core diameter. The core is the central part of the fiber, which is the medium for transmitting light signals. The cladding is the part that wraps around the core, which is the shielding layer that prevents light signals from leaking out.
Single-mode fiber: abbreviated as SMF, the core diameter is usually 9/125µm, that is, 9 microns, and the cladding diameter is 125 microns. Single-mode fiber can only transmit one mode of light, that is, the fundamental mode that propagates along the central axis of the fiber.
Multimode fiber: abbreviated as MMF, the core diameter is generally 50/125µm or 62.5/125 µm, that is, 50 or 62.5 microns, and the cladding diameter is 125 microns. Multimode fiber can transmit multiple modes of light, that is, higher-order modes that propagate along different paths.
Fiber transmission speed
Another difference between single-mode fiber and multimode fiber is their transmission speed. The transmission speed is affected by dispersion, which refers to the phase difference caused by different wavelengths or different modes of light in the transmission process, resulting in signal distortion and attenuation.
Single-mode fiber: Since single-mode fiber only has one transmission mode, there is no modal dispersion (also called intermodal dispersion), only a small amount of waveguide dispersion and material dispersion. Therefore, single-mode fiber has higher transmission speed and lower signal loss.
Multimode fiber: Since multimode fiber has multiple transmission modes, there is a large modal dispersion, as well as waveguide dispersion and material dispersion. Therefore, multimode fiber has lower transmission speed and higher signal loss.
Fiber transmission distance
The third difference between single-mode fiber and multimode fiber is their transmission distance. The transmission distance is affected by signal loss and bandwidth limitations.
Single-mode fiber: Since single-mode fiber has higher transmission speed and lower signal loss, it can support longer transmission distance. Usually, single-mode fiber can reach tens of kilometers or even hundreds of kilometers of transmission distance.
Multimode fiber: Since multimode fiber has lower transmission speed and higher signal loss, it can only support shorter transmission distance. Usually, multimode fiber can only reach hundreds of meters or a few kilometers of transmission distance.
Fiber usage range
The fourth difference between single-mode fiber and multimode fiber is their application range. The application range is affected by factors such as transmission speed, transmission distance, cost, etc.
Single-mode fiber: Single-mode fiber is suitable for high-speed and long-distance data transmission, such as telecommunications, cable TV, railways, military, financial securities and other fields. It is an ideal choice for broadband data networks and IP data transmission private networks.
Multimode fiber: Multimode fiber is suitable for low-speed and short-distance data transmission, such as local area networks, campus networks, data centers and other fields. It is an economical choice for broadband campus networks, broadband cable TV networks and intelligent broadband community fiber to the building and fiber to the home.
Fiber Optic Practical Use Cases
Here are three practical examples of using single-mode and multimode fibers:
Case one: A company needs to establish a high-speed network connection between two office buildings that are 20 kilometers apart. In order to ensure signal quality and stability, it chooses single-mode fiber as the transmission medium, using single-mode fiber transceivers and single-mode fiber jumpers to connect the switches of the two office buildings.
Case two: A school needs to deploy a wireless network covering the whole school in the campus. In order to save cost and improve efficiency, it chooses multimode fiber as the transmission medium, using multimode fiber transceivers and multimode fiber jumpers to connect the wireless access points on each floor.
Case three: An electric power company needs to install a video surveillance system on a 100-kilometer-long power transmission line. In order to ensure image clarity and real-time performance, it chooses single-mode fiber as the transmission medium, using single-mode fiber transceivers and single-mode fiber jumpers to connect the cameras at each monitoring point.