Fiber Optics MULTIMODE VS. SINGLEMODE FIBER
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…………
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
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.
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 stepindex fiber
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
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.
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.
Fiber Optics WHAT DO THE NUMBERS MEAN?
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
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.
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
Fiber Optics • What color is associated with 62.5um MM fiber? • What color is associated with 50um MM fiber? YELLOW AQUA
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.
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.