Difference Between Single Mode and Multi Mode Cables

Emerging demand of higher bandwidth and faster speed connections has significantly enhanced the growth of fiber optic cable assemblies market over the past several years, especially the single mode fiber (SMF) and multimode fiber cable (MMF). However, though these two types of fiber optic cables are widely used in diverse applications, the problem—single mode vs multimode fiber: what’s the difference—is still confusing. Therefore, the following article will focus on the basic construction, fiber distance, cost and fiber color, to make an in-depth comparison between single mode and multimode fiber.

Single Mode and Multimode Fiber Overview

Single mode means the fiber enables one type of light mode to be propagated at a time. While multimode means the fiber can propagate multiple modes. The difference between single mode and multimode fiber mainly lies in fiber core diameter, wavelength, light source and bandwidth.

Core Diameter

Single mode fiber core diameter is much smaller than multimode fiber. The typical core diameter is 9µm even if there are others available. And multimode fiber core diameter is 50µm and 62.5µm typically, which enables it has higher “light gathering” ability and simplify connections. The cladding diameter of single mode and multimode fiber is 125µm.

Wavelength & Light Source

Due to the large core size if multimode fiber, some low-cost light sources like LEDs (light-emitting diodes) and VCSELs (vertical cavity surface-emitting lasers) that works at the 850nm and 1310nm wavelength are used in multimode fiber cables. While the single mode often uses a laser or laser diodes to produce light injected into the cable. And the commonly used single mode fiber wavelength is 1310nm and 1550nm.

Bandwidth

Multimode fiber bandwidth is limited by its light mode and the maximum bandwidth at present is 28000MHz*km of OM5 fiber. While single mode fiber bandwidth is unlimited theoretically due to it allows one light of mode to pass through at a time.

Single Mode vs Multimode Fiber Distance

It’s known that single mode fiber is suitable for long distance applications, while multimode optical fiber is designed for short distance runs. Then when it comes to single mode vs multimode fiber distance, what’s the quantifiable differences?we can see as single mode fiber distance is much longer than that of multimode fiber cables at the data rate from 1G to 10G, but OM3/OM4/OM5 multimode fiber supports higher data rate. Because multimode optical fiber has a large core size and supports more than one light mode, its fiber distance is limited by model dispersion which is a common phenomenon in multimode step-index fiber. While single mode fiber is not. That’s the essential difference between them.

Single Mode vs Multimode Fiber Cost

“Single mode vs multimode fiber cost” is a hot topic in some forums. Numbers of people have expressed their own opinions. Their views mainly focus on the optical transceiver cost, system cost and installation cost.

Optical Transceiver Cost

Compared to single-mode transceivers, the price of multimode transceivers is nearly two or three times lower. The following table takes FS Cisco compatible single-mode transceivers and multimode transceivers as an example.

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