The diameter of the circle that circumscribes the core area.[Arr11] Core Size Mismatch
The signal insertion loss that occurs in a fiber optic connector due to the difference between the size of the fiber core in one connector compared to the size of the fiber core in the mating connector. The diagram below shows how the core size of fiber strands can vary. This example shows that the light from the larger core size will not be transferred to the fiber with the smaller core size. [Opt09]
An arrangement whereby two signal paths, one in each direction, exist in a ring topology. [Fib111]
Counter-Rotating Signal Path Illustration courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/c
In fiber optics, a device which links three or more fibers, providing two or more paths for the transmission signal. In an "active" coupler, a switching mechanism selects among several routes; in a "passive" coupler, routing is determined by the geometry of the device.[Arr11] An optical device that combines or splits power from optical fibers. [Fib111]
Fused Coupler Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/c
Coupling ratio or splitting ratio is defined as the ratio of the optical power from one output port of the coupler to the sum of the total power from all output ports. The coupling ratio is measured at the specified center wavelength and is normally expressed as a percentage. [AOF11] The ratio/loss of optical power from one output port to the total output power, expressed as a percent. For a 1 x 2 Wave Division Multiplex (WDM) or coupler with output powers O1 and O2, and Oi representing both output powers:
Continuous Power Bus. Provides downstream power and RF signal with tap faceplate removed.[Arr11]
CPD Common Path Distortion
CPE Customer Premises Equipment CPE Controlled Cable Modem
A cable modem in which a portion of the higher-layer processing is performed by an external device, in particular, by a PC.
CRA Certificate Requesting Authority
CRC Cyclic Redundancy Check; an error-detection scheme that (a) uses parity bits generated by polynomial encoding of digital signals, (b) appends those parity bits to the digital signal, and (c) uses decoding algorithms that detect errors in the received digital signal. Note: Error correction, if required, may be accomplished through the use of an automatic repeat-request (ARQ) system. Also, an error checking mechanism that checks data integrity by computing a polynomial algorithm based checksum. [INFOSEC-99] [ATI11]
Also referred to as peak-to-average ratio (PAR) or peak-to-average power ratio (PAPR); a measurement of a waveform, calculated from the peak amplitude of the waveform divided by the RMS value of the waveform.
It is therefore a dimensionless quantity. While this quotient is most simply expressed by a positive rational number, in commercial products it is also commonly stated as the ratio of two whole numbers, e.g., 2:1. In signal processing applications it is often expressed in decibels (dB). The minimum possible crest factor is 1, 1:1 or 0 dB. [Wik118]
This table provides crest factor values for some normalized waveforms:
Notes: 1. crest factors specified for QPSK, QAM, and WCDMA are typical factors needed for reliable communication, not the theoretical crest factors which can be larger.