Single mode fiber (SMF) and multimode fiber (MMF) optic cables are now widely used in diverse applications, but when it comes to installing fiber optic cabling, do you really know whether to install single mode or multimode? To thoroughly compare them, this article will focus on their basic construction, bandwidth, fiber color, etc.
Before we discuss each type of fiber, here are some definitions:
Optical fiber: The glass portion of a fiber optic cable – no jacketing or strength members included. An optical fiber is made up of a light carrying core surrounded by cladding. The cladding prevents light from escaping the core, effectively keeping the signal moving down the glass.
Single mode fiber: a fiber featuring a small light-carrying core of about 9 micrometers (µm) in diameter. For reference, a human hair is closer to 100 µm. The core is surrounded by a cladding that brings the overall diameter of the optical fiber to 125 µm.
Multimode fiber: a fiber with a core of 50 µm or above. A larger core means multiple modes (or rays of light) can travel down the core simultaneously. Just like single mode, the core is surrounded by a cladding that brings the overall diameter of the optical fiber to 125 µm.
In short, 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 differences between single mode and multimode fiber optic cable mainly lie in fiber core diameter, wavelength & light source, bandwidth, color sheath, etc,.
Single mode fiber core diameter is much smaller than multimode fiber, with 9 µm for single mode and 50 µm or 62.5 µm for multimode fiber. That means multimode fiber optic cables have higher "light gathering" ability and simplify connections. Although their core diameter is different, the cladding diameter of both is 125 µm.
Wavelength & Light Source
Multimode fiber cables use low-cost light sources that work at 850nm and 1300nm wavelength, such as LEDs (light-emitting diodes) and VCSELs (vertical cavity surface-emitting lasers), while single mode fiber cables use a laser or laser diodes to produce light injected into the cable, and the commonly used single mode fiber wavelength is 1310nm and 1550nm.
Limited by multimode fiber’s light mode, the maximum bandwidth of OM5 fiber is 28000MHz*km at present. For single mode fiber, the bandwidth is unlimited, because it allows only one light mode to pass through at a time.
According to the TIA-598C standard definition, for non-military applications, single mode cable is coated with yellow outer sheath, and multimode fiber is coated with orange or aqua jacket.
- There is no way to distinguish between single mode and multimode optical fibers with the naked eye. Standard optical fibers, as mentioned above, have cladding around the core that brings the diameter of the optical fiber itself to 125 µm. What you can see when you put a connector on an optical fiber are the cladding and any integral protective coating.
- The terms “single mode” and “multimode” also have no relation to the number of optical fibers in the fiber optic cable you are running. It’s possible to have a cable containing 144 single mode optical fibers, and it’s also possible to have a cable containing 144 multimode optical fibers.
- There is no such thing that single mode optical fibers are better than multimode ones. Both have their own advantages, for example, single-mode optical fiber holds advantages in terms of bandwidth and reach for longer distances, multimode optical fiber easily supports most distances required for enterprise and data center networks. Just choosing the best-fit one for your applications is ok.
- Single mode and multimode fiber can’t be mixed, since they are different in core size and the number of light modes. If you mix the two fibers, you’ll lose a large amount of optical loss, resulting in a link flapping or being down. Keep in mind that never mix different types of cabling randomly.
Single mode fiber has a smaller core than multimode and is suitable for long haul installations, and it’s generally more expensive. Multimode fiber cabling system has a shorter reach and is widely deployed in enterprise, data centers and LANs. When making a decision between single mode and multimode fiber cables, choose the one that best suits your network demands.
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About AV Access
AV Access is an experienced manufacturer that produces quality HDMI extenders, KVM extenders, wireless presentation systems, etc. and we also offer AV over IP solutions for scalable uses. These products — HDBaseT extender, and 4K HDMI extender — are among our best-sellers.