It is important to use an electronic driver which is both well matched to the EOM and suitable for the particular application. For example, different kinds of EOMs require different drive voltages, and the driver should also be designed for the given electrical capacitance of the EOM. Some drivers are suitable for a purely sinusoidal modulation, whereas broadband devices work in a large range of modulation frequencies. Many problems can be avoided by purchasing an electro-optic modulator together with the electronic driver from the same supplier, because the responsibility for the overall performance is then at one place.
Some typical applications of electro-optic modulators are:
modulating the power of a laser beam, e.g. for laser printing, high-speed digital data recording, or high-speed optical communications
in laser frequency stabilization schemes, e.g. with the Pound–Drever–Hall method
Q switching of solid-state lasers (where the EOM serves to block the laser resonator before the pulse is to be emitted)
active mode locking (where the EOM modulates the resonator losses or the optical phase with the round-trip frequency or a multiple thereof)
switching pulses in pulse pickers, regenerative amplifiers and cavity-dumped lasers [Enc11]
Electronic Program Guide
EdgeQAM Modulator; a head end or hub device that receives packets of digital video or data. It re-packetizes the video or data into an MPEG transport stream and digitally modulates the digital transport stream onto a downstream RF carrier using quadrature amplitude modulation (QAM). [Cab112]
The offering of access to local exchange facilities on a non-discriminatory basis.
Equilibrium Mode Distribution
The steady modal state of a multimode fiber in which the relative power distribution among modes is independent of fiber length. [Fib111]
A means of modifying the frequency and/or phase response of an amplifier or network, thereby resulting in a flat overall response. Or, the spacing and operation of amplifiers, so that the gain provided by the amplifier, per transmission frequency, coincides with the signal loss at the same frequency within communications devices. Equalization is achieved by circuitry that compensates for the differences in attenuation at different frequencies. [Arr11]
Any loss in cable television systems caused by coaxial cable; also, insertion loss of components designed to match cable loss characteristics.
Equalizer, Cable (EQ)
A network device designed to compensate for the frequency/ loss characteristics of a cable, so as to permit the system to pass all frequencies in a uniform manner. [Arr11]
Pulses of one half the width of the horizontal sync pulses which are transmitted at twice the rate of the horizontal sync pulses during the blanking intervals immediately preceding and following the vertical sync pulses. The action of these pulses causes the vertical deflection to start at the same time in each interval, and also serves to keep the horizontal sweep circuits in step during the vertical blanking intervals immediately preceding and following the vertical sync pulse.
An orbit with a plane parallel to the earth's equator. [Sat07]
Extinction Ratio; applies to optical intensity laser modulators. ER characterizes the efficiency of the modulator to transmit light when in an “ON” state and block light in an “OFF” state. Two different extinction ratios are defined: DC extinction ratio and RF dynamic extinction ratio (DER). [Jer04]
DC Extinction Ratio; measured with no electrical signal applied on the RF input port of an intensity modulator. The bias voltage on the DC port (connected to the DC electrode) is adjusted to achieve an “ON” state (Pout is maximum) then an “OFF” state (Pout is minimum). ERDC is measured as the ratio of Poutmax over Poutmin and is expressed in dB. [Jer04]
In digital transmission systems, a scheme that adds overhead to the data to permit a certain level of errors to be detected and corrected. [Fib111]
Checking for errors in data transmission. A calculation based on the data being sent; the results of the calculation are sent along with the data. The receiver then performs the same calculation and compares its results with those sent. If the receiver detects an error, it can be corrected, or it can simply be reported. [Fib111]
A measure of the performance of a digital transmission system. It can be specified as a bit error rate (the probability of error per bit transmitted), as a block error rate (the probability of one or more errors in a specified-length block of bits), or in other forms such as percent error-free seconds.
Any 1-sec interval containing at least one bit error.
Engineering Service Circuit; the 300-3,400 Hertz voice plus teletype (S+DX) channel used for earth station-to-earth station and earth station-to-operations center communications for the purpose of system maintenance, coordination and general system information dissemination. In analog (FDM/FM) systems there are two S+DX channels available for this purpose in the 4,000-12,000 Hertz portion of the baseband. In digital systems there are one or two channels available which are usually convened to a 32 or 64 Kbps digital signal and combined with the earth station traffic digital bit stream. Modern ESC equipment interfaces with any mix of analog and digital satellite carriers, as well as backhaul terrestrial links to the local switching center. [Sat07]
Enterprise Systems Connection; a duplex optical connector used for computer-to-computer data exchange. [Fib111]
Electrostatic Discharge. Static discharge which may damage electronic equipment. [Arr11]
Embedded Subscriber Media Gateway
The most popular LAN technology in use today. The IEEE standard 802.3 defines the rules for configuring an Ethernet network. It is a 10Mbps, 100Mbps, or 1000 Mbps CSMA/CD baseband network that runs over thin coax, thick coax, twisted pair or fiber optic cable.
Ethernet Diagram courtesy of fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/e
European Telecommunications Standard. Prefix for certain ETSI documents.
European Telecommunications Standards Institute
Enhanced Television. A general term that refers to interactive services and applications provided in conjunction with video programming.
Educational Television Station
As frequency allocation band plans differ between U.S. and European CATV systems, DOCSIS standards have been modified for use in Europe. These changes were published under the name of "EuroDOCSIS". The main differences account for differing TV channel bandwidths; European cable channels conform to PAL TV standards and are 8 MHz wide, whereas in North America channels conform to ATSC standards which specify 6 MHz. The wider bandwidth in EuroDOCSIS architectures permits more bandwidth to be allocated to the downstream data path (toward the user). EuroDOCSIS certification testing is executed by Excentis (formerly known as tComLabs), while DOCSIS® certification testing is executed by CableLabs. Typically, customer premises equipment (CPE) receives "certification", while CMTS equipment receives "qualification". Most cable systems in Japan and Colombia utilize the North American version of DOCSIS®, while some employ a variant of DOCSIS® that uses upstream channels that are based on a 9.216 MHz master clock (as opposed to 10.24 MHz used in DOCSIS®/EuroDOCSIS) resulting in upstream channel widths that are a power-of-two division of 6 MHz (as opposed to 6.4 MHz in DOCSIS®/EuroDOCSIS). The ITU Telecommunication Standardization Sector (ITU-T) has approved the various versions of DOCSIS® as international standards. While ITU-T Recommendation J.112 Annex B corresponds to DOCSIS®/EuroDOCSIS 1.1, Annex A describes an earlier European cable modem system ("DVB EuroModem") based on ATM transmission standards. Annex C describes a variant of DOCSIS® 1.1 that is designed to operate in Japanese cable systems. The ITU-T Recommendation J.122 main body corresponds to DOCSIS® 2.0, J.122 Annex F corresponds to EuroDOCSIS 2.0, and J.122 Annex J describes the Japanese variant of DOCSIS® 2.0 (analogous to Annex C of J.112).
European Norms (EN)
Prefix for certain European Telecommunications Standards Institute (ETSI) documents.
European Telecommunications Standards Institute (ETSI)
The European equivalent of ANSI (American National Standards Institute).
The European Telecommunications Satellite Organization which is headquartered in Paris, France. It provides a satellite network for Europe and parts of North Africa and the Middle East. [Sat07]
Light guided in the inner part of an optical fiber’s cladding rather than in the core, i.e. the portion of the light wave in the core that penetrates into the cladding. [Fib111]
Evanescent Wave Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/e
A message capturing a single portion of a connection.
Events are asynchronous communication between applications and the OpenCable system on which they are being executed. They provide communication between solution elements. An event may also refer to a unit of programming, such as a movie, an episode of a television show, a newscast or a sports game.
Error Vector Magnitude; a measurement of demodulator performance in the presence of impairments. The measured symbol location obtained after decimating the recovered waveform at the demodulator output is compared against the ideal symbol locations. The root-mean-square (RMS) EVM and phase error are then used in determining the EVM measurement over a window of N demodulated symbols. As shown below, the measured symbol location by the demodulator is given by w. However, the ideal symbol location (using the symbol map) is given by v. Therefore, the resulting error vector is the difference between the actual measured and ideal symbol vectors, i.e., e=w–v. [Zon10] The error vector e for a received symbol is graphically represented as follows:
Graphical Representation of Error Vector
In Figure above,
v is the ideal symbol vector,
w is the measured symbol vector,
w–v is the magnitude error,
θ is the phase error,
e=w–v) is the error vector, and
e/v is the EVM.
Excess loss is the ratio of the optical power launched at the input port of the coupler to the total optical power measured from all output ports, expressed in dB. [AOF11]
The provision in a commercial television film contract that grants exclusive playback rights for the film or episode to a broadcast station in the market it serves. Under the FCC's rules cable operators cannot carry distant signals which violate local television stations' exclusivity agreements.
Execution Engine (EE)
The portion of the OpenCable Platform which will provide a full programming environment for performing complex logic and arithmetic operations which the Presentation Engine (PE) cannot handle alone. In the EE, which will include Sun's JavaTV programming environment, ITV developers will write interactive applications, in Java, following the OCAP specification. When a cable customer with an OpenCable-compliant set-top box accesses the application through the user interface, the application is transparently downloaded into the box. A Java engine or JAVA Virtual Machine (JVM) resident in the set-top decodes the application downloaded over the network, and runs it. Or the execution engine is a platform- independent interface that permits programmatic content as part of the OpenCable Application Platform.
A frequency division scheme that allows bi-directional traffic on a single coaxial cable. Reverse path signals come to the headend from 5 to 42 MHz. Forward path signals go from the headend from 50 or 54 MHz to the upper frequency limit.
Extensible Hypertext Mark-up Language (XHTML)
A reformulation of HTML in XML. XHTML is a family of current and future document types and modules that reproduce, subset, and extend HTML 4. XHTML family document types are XML based, and ultimately are designed to work in conjunction with XML-based user agents.
This adapter is used when sufficient cable is not available for installation. 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]
Modulation of a light source by an external device that acts like an electronic shutter. [Fib111]
The sum of the absorption coefficient and the scattering coefficient. [From Weik '89] [ATI11]
Measured when the input polarization is aligned to the fast axis of the input fiber and usually expressed in dB. Sometimes referred to as Polarization Crosstalk. [AOF11] Also, the ratio of the “LOW”, or “OFF” optical power level (PL) to the “HIGH”, or “ON” optical power level (PH). Extinction ratio (%) ≡ (PL/PH) * 100. [Fib111]
A diagram that shows the proper function of a digital system. The “openness” of the “eye” refers to the achievable bit error rate (BER). [Fib111]
Eye Pattern courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/e