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Comparison Single-Mode Fiber and Multimode Fiber

November 10,2021

The basic structure of optical fiber generally consists of outer sheath, cladding, core, and light source. The following differences exist between single-mode and multimode optical fiber.

OUTER JACKET COLOR DIFFERENCE

In practical applications, the color of the outer jacket of an optical fiber can be used to quickly distinguish between single-mode and multimode fibers. According to the TIA-598C standard, single-mode fiber OS1 and OS2 use yellow outer jacket, multimode fiber OM1 and OM2 use orange outer jacket, and OM3 and OM4 use aqua outer jacket (under non-military use).

SINGLE AND MULTIMODE FIBER OUTER SHEATH COLOR

FIBER CORE DIAMETER DIFFERENCES

There is a significant difference in core diameter between multimode and single mode fibers, with multimode fibers typically having a core diameter of 50 or 62.5 µm and single mode fibers having a core diameter of 9 µm. Given this difference, single mode fibers can only transmit optical signals at wavelengths of 1310 nm or 1550 nm on a narrower core diameter, but the advantage of a small core is that the optical signal travels in a straight line in single mode fibers without refraction and with less dispersion. Refraction occurs, the dispersion is small, high bandwidth; multimode fiber core wide, it can transmit a variety of modes at a given working wavelength, but at the same time, because the multimode fiber in the transmission of up to hundreds of modes, the propagation constant and group rate of each mode is different, so that the fiber bandwidth is narrow, dispersion is large, loss is also large.

SINGLE MULTIMODE FIBER CORE DIAMETER DIAGRAM

Note: The standard cladding diameter of most optical fibers is 125um, and the standard outer protective layer diameter is 245um, without distinguishing between single and multimode.

THE DIFFERENCE OF LIGHT SOURCE

There are usually two kinds of light sources: laser light source and LED light source. Single-mode fiber uses laser light source and multimode fiber uses LED light source.