Some examples of applications of phase modulators are:
A phase modulator within a laser resonator of a single-frequency laser can be used for wavelength tuning, or for active mode locking (FM mode locking) of a laser.
A phase modulation of a beam with moderate modulation strength is often used in laser frequency stabilization schemes, e.g. with the Pound–Drever–Hall method.
Various kinds of interferometers and setups for spectroscopic measurements require phase modulators, often with a periodic drive signal.
Some metrology applications require frequency combs, generated by sending a single-frequency beam into a phase modulator. In that case, the phase modulation often needs to be strong in order to obtain a large number of optical sidebands.
In data transmitters of optical fiber communication systems, phase modulators can be used for encoding the transmitted information. An example is the method of phase shift keying. [Enc11]
Rapid, short-term, random fluctuations in the phase of a wave caused by time-domain instabilities in an oscillator. [Fib111] Phase Shift
Any device which is capable of transforming a measurable quantity of intelligence (such as sound) into relative electrical signals, e.g. a microphone. [Arr11] Phase-shift Keying (PSK)
1) In digital transmission, angle modulation in which the phase of the carrier discretely varies in relation, either to a reference phase or to the phase of the immediately preceding signal element, in accordance with data being transmitted. 2) In a communications system, the representation of characters, such as bits or quaternary digits, by a shift in the phase of an electromagnetic carrier wave with respect to a reference, by an amount corresponding to the symbol being encoded. Also called biphase modulation, phase-shift signaling. [Fib111]
A type of antenna design that incorporates two or more elements that integrate signal information received from the spatially separate elements, and that transmit in a coordinated manner (either simultaneously or alternately).
Pseudomorphic High Electron Mobility Transistor; an III-V compound semiconductor based device in the field effect transistor (FET) category of devices. [Fre11] PHILA
POD Host Interface License Agreement
Losing an electrical charge on exposure to light. [Fib111] Photodetector
Any device which detects light, generally producing an electronic signal with intensity proportional to that of the incident light. [Arr11]
A semiconductor device that converts light to electrical current. Photodiodes are used for the detection of optical power and for the conversion of optical power to electrical power. [Arr11]
A quantum of electromagnetic energy. [Arr11] A particle of light. [Fib111]
A term coined for devices that work using photons, analogous to the electronic for devices working with electrons. [Fib111] Photoresistor
A device that exhibits a variable resistance, depending on the amount of light that strikes it. Photovoltaic
Providing an electric current under the influence of light or similar radiation. [Fib111]
PHY Physical Layer
Physical (PHY) Layer
Layer 1 in the Open System Interconnection (OSI) architecture; the layer that provides services to transmit bits or groups of bits over a transmission link between open systems and which entails electrical, mechanical and handshaking procedures.
Physical Media Dependent (PMD) Sublayer
A sublayer of the physical layer which is concerned with transmitting bits or groups of bits over particular types of transmission link between open systems and which entails electrical, mechanical and handshaking procedures.
A prefix denoting one millionth of a millionth of a millionth; one trillionth (10-12). Pronounced "pie-ko." [Arr11]
Also referred to as a fiber pigtail. A short length of optical fiber, permanently fixed to a component, used to couple lightwave power between it and the transmission fiber. [Arr11] Fiber-coupled laser diodes – one with pulsed LD and one with CW laser diode; photo courtesy of Laser Components, http://www.lasercomponents.com/uk/company/
PII Personal Identifiable Identification Pilot Carrier
Signals on cable TV systems used to operate attenuation (gain) and frequency response (slope) compensating circuitry in amplifiers. [Arr11] Pilot Signal
A continuous wave (CW) signal, either modulated or unmodulated, transmitted on a network to provide control for various amplifier and monitor functions. [Arr11] PIN Photodiode
A diode with a large intrinsic region sandwiched between p-doped and n-doped semiconducting regions. Photons absorbed in this region create electron-hole pairs that are then separated by an electronic field, thus generating an electric current in a load circuit. [Arr11] Pin Type Connector
This connector is used on hard line cable. It has a pin which seizes and retains the cable center conductor. The pin then extends through the body and is retained within the equipment housing. [Arr11]
PING Packet Internet Grouper
One of many monochrome or color “dots” that make up a television picture.
A cathode-ray tube used to produce an image by variation of the intensity of a scanning beam.
An abbreviation of the term “picture element.” A pixel is the smallest picture element of a digital image; the smallest unit that can be displayed on a monitor. Like the fibers of a fabric, individual pixels are too small to notice, but together they make up the whole. The smaller the pixels, the higher the resolution. All images are composed of pixels.
PKCROSS Public Key Cryptography for Cross-Ream Authentication
PKCS Public Key Cryptography Standards
PKI Public Key Infrastructure
PKINIT Public Key Cryptography for Initial Authentication
Plain Old Telephone Service (POTS)
This term often is used to refer to analog voice telephone services provided over the public switched telephone network.
The original (unencrypted) state of a message or data. Also called cleartext.
A waveguide fabricated in a flat material such as thin film. [Fib111] Plant
A general term applied to any of the physical property of a service company which contributes to the furnishing of power or communication services. Also referred to as cable plant. [Arr11] Plastic Clad Silica (PCS)
Also called hard clad silica (HCS). A step-index fiber with a glass core and plastic or polymer cladding instead of glass. [Fib111] Plastic Fiber
An optical fiber having a plastic core and plastic cladding. [Fib111]
Plastic Optical Fiber (POF)
A plastic cable used, for short distances only, as an alternative to fiber optic cable. Although plastic is not as transparent as glass, it is more malleable and less expensive. POF is a possible choice for indoor networking. PLC
Planar Lightwave Circuit; a device which incorporates a planar waveguide. [Fib111] Plenum
The air handling space between walls, under structural floors, and above drop ceilings, which can be used to route intrabuilding cabling. [Fib111]
A type of cable that is commonly used in forced air plenums, or ducts. Plenum cable is made of a fire-retardant material that generates little or no smoke, so that if it catches fire, it will not circulate toxic smoke through the vent system. [Arr11] Plug-and-Play
An Intel-developed hardware standard created to automate the setup and configuration of hardware devices connected to a computer. In theory, it allows you to “plug” a device into the computer and “play” it without going through a complicated setup process.
A plug-in refers to a set of functionality which can be added to a generic platform in order to provide interpretation of DVB registered, but non-DVB-J, application formats. For example, HTML3.2 or MHEG-5 are examples of plug-ins.
A plug-in application refers to an application that conforms to an application format for which a plug-in has been registered with DVB and which is only interoperable within terminals which have the appropriate plug-in resident or connected to networks where an appropriate plug-in is being broadcast.
PMA Performance Monitoring Application
PMD Physical Media Dependent Sublayer
Polarization Mode Dispersion [Fib111]
Public Switched Telephone Network Media Gateway
PMT Program Map Table
POD Point-of-Deployment Module, now called a CableCARD
POF Plastic Optical Fiber Point-of-Deployment (POD) Module
Now referred to as CableCARDs. See also CableCARD™.
The point where the inter-exchange carrier's responsibilities for the line begin and the local exchange carrier's responsibility ends. Location of a communications carrier's switching or terminal equipment.
A circuit connecting two nodes only, or a configuration requiring a separate physical connection between each pair of nodes.
Point-to-Point Protocol (PPP)
A method of transmitting TCP/IP and other networking protocols over a dial-up or WAN connection.
Transmission between two designated stations. [Fib111]
Point-to-Point Transmission Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/p
An antenna mount that permits all satellites in the geosynchronous arc to be scanned with movement of only one axis. [Arr11] Polarization
A characteristic of the electromagnetic wave. Four senses of polarization are used in satellite transmission: horizontal, vertical, right-hand circular and left-hand circular. [Arr11]
Polarization Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/p
Polarization Dependent Loss (PDL)
The performance of a coupler can vary slightly depending on the direction of polarization of light in the fiber. Polarization Dependent Loss (PDL) is the maximum change in the insertion loss of a coupler as the input polarization to the coupler is varied through all states of polarization (SOP). [AOF11] Polarization Maintaining Couplers (PMC)
Polarization Maintaining Couplers (PMC) are made from Polarization Maintaining Fiber (PMF) and are designed to maintain the polarization state between the input and the output fibers of the coupler. The extinction ratio of a PMC is a measure of how well the polarization state is maintained and is the ratio between the slow and the fast polarization axes on an output port of the coupler. [AOF11] Polarization Maintaining Fiber
Fiber designed to propagate only one polarization of light that enters it. [Fib111]
Polarization Maintaining Fiber Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/p