Handbook for Sound Engineers

482 Chapter 15

Multimode Distortion: The signal distortion in an opti-
cal waveguide resulting from the superposition of
modes with differing delays.

Multimode Fiber: Optical waveguide whose core
diameter is large compared with the optical wavelength
and in which, consequently, a large number of modes
are capable of propagation.

Nanometer (nm): One billionth of a meter (1 ×
10 –9m).

Noise Equivalent Power (NEP): The rms value of
optical power that is required to produce an rms SNR of
1; an indication of noise level that defines the minimum
detectable signal level.

Numerical Aperture: A measure of the range of angles
of incident light transmitted through a fiber. Depends on
the differences in index of refraction between the core
and the cladding.

Optical Fiber Class (OM1, OM2, OM3, and OS1 de-
signations in accordance with ISO11801: Bandwidth
and the maximum transmission distance of different
optical fiber classes for 10G Ethernet application,
Table 15-6.

Optical Time Domain Reflectometer (OTDR): A me-
thod for characterizing a fiber wherein an optical pulse
is transmitted through the fiber and the resulting back-
scatter and reflections to the input are measured as a
function of time. Useful in estimating the attenuation
coefficient as a function of distance and identifying de-
fects and other localized losses.

Optoelectronic: Any device that functions as an electri-

cal-to-optical or optical-to-electrical transducer.

Optoelectronic Integrated Circuits (OEICs): Combi-

nation of electronic and optical functions in a single chip.

Peak Wavelength: The wavelength at which the optical

power of a source is at a maximum.

Photocurrent: The current that flows through a photo-

sensitive device, such as a photodiode, as the result of

exposure to radiant power.

Photodiode: A diode designed to produce photocurrent

by absorbing light. Photodiodes are used for the detec-

tion of optical power and for the conversion of optical

power into electrical power.

Photon: A quantum of electromagnetic energy.

Pigtail: A short length of optical fiber for coupling opti-

cal components. It is usually permanently fixed to the

components.

PIN-FET Receiver: An optical receiver with a PIN

photodiode and low noise amplifier with a high imped-

ance input, whose first stage incorporates a field-effect

transistor (FET).

PIN Photodiode: A diode with a large intrinsic region

sandwiched between p-doped and n-doped semicon-

ducting regions. Photons in this region create electron

hole pairs that are separated by an electric field thus

generating an electric current in the load circuit.

Plastic Optical Fiber (POF): An optical fiber com-

posed of plastic instead of glass. POFs are used for short

distances of typically 25 ft or less.

Table 15-6. Bandwidth and the Maximum Transmission Distance of Different Optical Fiber Classes for 10G
Ethernet Application

Fiber Type Bandwidth 850 nm

MHz*km

Bandwidth 1300 nm

MHz*km

1 Gbps Transmission

Distance

10 Gbps Transmission

Distance

Fiber

Class

Multimode @850 nm @1300 nm @850 nm @1300 nm

Traditional 62.5/125ȝm 200 500 275 m 550 m 33 m 300 m OM1

Traditional 50/125ȝm 400 800 500 m 1000 m 66 m 450 m OM1

Traditional 50/125/62.5ȝm 500 500 550 m 550 m 82 m 300 m OM2

50/125ȝm-110 600 1200 750 m 2000 m 110 m 850 m OM2+

50/125ȝm-150 700 500 750 m 550 m 150 m 300 m OM2

50/125ȝm-300 1500 500 1000 m 550 m 300 m 300 m OM3

50/125ȝm-550 3500 500 1000 m 550 m 550 m 550 m NA

Single Mode @1310 m @1550 nm 1310/1383/1550 nm

Traditional 9/125ȝm 5000 m 10000 m–40000 m OS1