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Fiber Optics

MULTIMODE VS. SINGLEMODE FIBER

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Fiber Optics

When we talk about fiber we refer to either multimode or singlemode fiber.

We further clarify the types by their core and cladding size.

The core and cladding numbers will be listed on the cable jackets…………

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Fiber Optics

The standard core and cladding size for multimode fiber is 62.5/125

A new multimode standard (OM3) that uses an optimized laser transmissions system has a core and cladding size of 50/125.

The standard core and cladding size for singlemode fiber is

8.3/125

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Fiber Optics

The 62.5/125um MM standard is color coded orange.

The 50/125um MM standard is color coded aqua.

The 8.3/125um SM standard is color coded yellow.

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Fiber Optics

The terms multimode and singlemode refer to how light signals are transmitted through a fiber.

Single mode fiber uses a single mode of transmitting data

The data flows down a solid core of glass

This glass is referred to as step index fiber

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Fiber Optics

Multimode fiber utilizes multiple modes of transmitting data thru the glass

The glass core is comprised of multiple layers of glass

This type of glass core is called graded index

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Fiber Optics

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Fiber Optics

In graded index fiber the signal is sent down each layer of glass, allowing for multiple modes of transmission.

The graded index of MM fiber is quoted as only one core size i.e. 62.5um or 50um both of which have multiple layers of glass.

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Fiber Optics

There is MM fiber with larger step index cores (solid glass cores) that are used for low speed LANs.

We see this application in home theater systems that use fiber for audio, these are very short distance fibers that are typically used as a patch cord.

The smaller the core the further the light can travel without as much light dispersion loss.

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Fiber Optics

WHAT DO THE NUMBERS MEAN?

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Fiber Optics

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Fiber Optics

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Fiber Optics

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Fiber Optics

The cladding is the same size for all three fiber types at 125 microns (micro meter).

When stripping fiber for termination remember that the cladding is not stripped off.

900um MM fiber has another layer which is the actual jacketing that will be color coded to indicate the fiber color code sequence

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Fiber Optics

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Fiber Optics

SM fiber is 250um which is very thin, the buffer material is color coded which keeps the overall diameter small.

MM mode fiber can also have a 250um buffer, this smaller sized fiber is normally found in outside plant cabling and many times under the same jacketing with SM fiber and would require a break out kit to facilitate terminations.

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Fiber Optics

The colors associated with multimode and singlemode mostly apply to the patch cords, though MC (metallic clad) cables will also be color coded to distinguish the different modes.

What color is associated with singlemode?

YELLOW

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Fiber Optics

What color is associated with 62.5um MM fiber?

What color is associated with 50um MM fiber?

YELLOW

AQUA

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Fiber Optics

Singlemode fiber uses lasers to transmit signals through the core, lasers in conjunction with the smaller core size allows the light to travel much further.

The light will propagate down the fiber for 26km or 15.1 miles before the signal has to be repeated.

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Fiber Optics

Multimode uses LEDs to transmit light signals through the fiber core, this limits the distance that the light will travel.

The maximum length of a MM cable run is 2000 meters.

The LED light used is red and will not affect your eyes if you look directly at, with lasers the light is in a spectrum invisible to the human eye and can cause damage to your sight.