Common Terms

CATV

Insertion Loss: The loss of signal power resulting from the insertion of a device in a transmission line.  Insertion loss is expressed in decibels (dB).  The lower the value, the better the performance.

Return Loss (aka reflection loss): The loss of signal power caused by the reflection of the signal by a device back toward the source.  Return loss is expressed in decibels (dB).  The higher the value, the better matched the connected devices are.  This in turn lowers the insertion loss, improving the function of the devices.  The return loss can be used in different configurations, including input/output/tap return loss, which measures the return loss on all ports on the unit.  A low return loss can occur when unused F ports are not terminated.

Tap Loss (DTLG):  The loss of signal between the input and the tap.

Isolation:  This refers to the electrical signal measurement between any output ports.  The higher the isolation, the better the electrical signal separation between the output ports.  This means less signal interference from one port to another.  Isolation is expressed in decibels (dB).  The isolation is often listed in different configurations, including tap to tap isolation (taps), output to tap isolation (taps) and output to output isolation (splitters)

Hum Modulation: The distortion caused by the modulation of the electrical RF signal from the device components passing AC power.  It is commonly measured using a current of 10 amps and is displayed in decibels (dB).

RFI Shielding: Radio Frequency Interference (RFI) is disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source.  The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of the circuit. These effects can range from a simple degradation of data to a total loss of data.  Shielding against RFI is achieved by using a solder back, thus preventing interference entering the product.  RFI shielding is measured in dB, with a lower value representing a higher shielding.

Resistance: The electrical resistance of a product measures its opposition to the passage of an electric current.  The unit of measurement for electrical resistance is the ohm (Ω).  The higher the resistance, the higher the opposition to passing current and thus, the worse the performance of the unit.

Forward Gain: The gain is a measure of the ability of an amplifier to increase the amplitude of a signal from the input port to the output port.  A higher gain signifies a higher amplitude and thus, a stronger signal coming out of the unit than was put into it.

Return Gain: The return gain is a measure of the ability of an amplifier to increase the amplitude of a signal from the input port to the output port and back again.  Return gain is useful in applications that require two way service i.e. pay per view/ on demand services, online gaming and web streaming.

Noise Figure: The noise figure is the difference in decibels (dB) between the noise output of the actual receiver to the noise output of an “ideal” receiver with the same overall gain and bandwidth when the receivers are connected to matched sources at the standard noise temperature.  It is a measure of degradation of the signal-to-noise ratio (SNR), caused by components in the RF signal chain.

Fiber

Output Wavelength: XXXXX

Laser Type: The laser type is the name given to the specific laser used in a unit.  This can be either a Fabry-Perot (FP) laser or a distributed feedback (DFB) laser.  The FP laser operates at wavelengths 1310, 1480 and 1550 but transfers data less efficiently than the DFB laser.  The DFB laser works at more wavelengths and has a higher data transfer rate.  Due to these operational differences, the FP laser type is the more economical.

Optical Return Loss: The loss of signal power caused by the reflection at a discontinuity in a transmission line.  Return loss is expressed in decibels (dB).  The higher the value, the better matched the connected devices are.  This in turn lowers the insertion loss, improving the function of the devices. 

RF Bandwidth: Bandwidth is the difference between the upper and lower frequencies in a contiguous set of frequencies. It is measured in Hertz (Hz).  The unit typically operates between the upper and lower bandwidths only.  Outside of these values, the unit will cease to operate as designed.

RF Input Level: The level of the RF signal sent into the transmitter unit.  This is measured in dBmV.  The RF signal level at most receiver terminals is 0dBmV, which is significantly less than the RF Input level of devices closer to the transmission source in the network.

RF Return Loss: The loss of signal power caused by the reflection at a discontinuity in a transmission line.  Return loss is expressed in decibels (dB).  The higher the value, the better matched the connected devices are.  This in turn lowers the insertion loss, improving the function of the devices. 

CNR: Carrier to noise ratio is the signal-to-noise ratio (SNR) of a modulated signal. The term is used to distinguish the CNR of the radio frequency passband signal from the SNR of an analogue base band message signal after demodulation.  Digitally modulated signals are made of two CW carriers (the I and Q components, which are out-of-phase carriers).  The information (bits or symbols) is carried by given combinations of phase and/or amplitude of the I and Q components.  It is for this reason that digitally modulated signals are usually referred to as carriers.  A high CNR provides good quality of reception.

CTB: Composite Triple Beat is a combination (composite) of a number of third order distortions that are generated by non linearites within amplifiers and other components in a cable TV network handling many RF signals. It is a form of coherent distortion.

Link Loss: The total measured power loss of a fiber optic point to point span or link.  The loss is the result of intrinsic attenuation plus extrinsic discontinuities in a fiber optic cable.  Link loss is wavelength depedent and measured in decibels per kilometer or dB km.  The higher the loss, the lower the power and thus, the poorer the performance of the unit.

Optical Input Range: This refers to the range of input XX (signals, power, wavelengths?) which the optical receiver unit can receive from the transmitter.  This is measured in dBm.