IEC 60728-6-2003 pdf – Cable networks for television signals, sound signals and interactive services – Part 6: Optical equipment.
1 Scope This part of IEC 60728 lays down the measuring methods, performance requirements and data publication requirements of optical equipment of cable networks for television signals, sound signals and interactive services. This standard • applies to all optical transmitters, receivers, amplifiers, directional couplers, isolators, multiplexing devices, connectors and splices used in cable networks; • covers the frequency range 5 MHz to 3 000 MHz; NOTE The upper limit of 3 000 MHz is an example, but not a strict value. The frequency range or ranges, over which the equipment is specified, shall be published. • identifies guaranteed performance requirements for certain parameters; • lays down data publication requirements with guaranteed performance; • describes methods of measurement for compliance testing. All requirements and published data relate to minimum performance levels within the specified frequency range and in well-matched conditions as might be applicable to cable networks for television signals, sound signals and interactive services. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60068-1, Environmental testing. Part 1: General and guidance IEC 60068-2, (all parts), Environmental testing – Part 2: Tests IEC 60169-2, Radio-frequency connectors – Part 2: Coaxial unmatched connector IEC 60169-24, Radio-frequency connectors – Part 24: Radio-frequency coaxial connectors with screw coupling, typically for use in 75 ohm cable distribution systems (Type F) IEC 60417-DB:2002 * , Graphical symbols for use on equipment IEC 60529, Degrees of protection provided by enclosures (IP Code) IEC 60617 (all parts) [DB]*, Graphical symbols for diagrams
3.1.2 optical receiving unit; optical receiver; Rx (abbreviation) receive fibre optic terminal device accepting at its input port a modulated optical carrier, and providing at its output port the corresponding demodulated electrical signal (with the associated clock, if digital) NOTE For the purposes of this standard, optical receivers may have more than one output port providing electrical RF signals. [IEC 61931, definition 2.9.7] 3.1.3 optical amplifier optical waveguide device containing a suitably pumped, active medium which is able to amplify an optical signal [IEC 61931, definition 2.7.75] 3.1.4 (optical) isolator two port non-reciprocal optical device intended to suppress backward reflection, while having minimum insertion loss in the forward direction, based on Faraday effect NOTE 1 An isolator is commonly used to prevent return reflections along a transmission path. NOTE 2 An isolator is generally polarization dependent; however fibre optic polarization independent isolators exist. [IEC 61931, definition 2.6.30] 3.1.5 (optical (fibre)) splice permanent, or semi permanent, joint whose purpose is to couple optical power between two optical fibres [IEV 731-05-05 modified] [IEC 61931, definition 2.6.8] 3.1.6 fibre optic branching device; (optical) (fibre) branching device; (optical) (fibre) coupler (deprecated)] optical fibre device, possessing three or more optical ports, which shares optical power among its ports in a predetermined fashion, at the same wavelength or wavelengths, without wavelength conversion NOTE The ports may be connected to fibres, sources, detectors, etc. [IEC 61931, definition 2.6.21] 3.1.7 directional branching device; directional coupler (deprecated) device which distributes an optical signal among the output ports in a predetermined fashion only when light is launched into one preselected input port [IEC 61931, definition 2.6.22] NOTE For the purposes of this standard, directional coupler is the preferred term because this is also the term for its electrical equivalent.
3.1.22 coherence time time over which a propagating light may be considered to be coherent radiation [IEV 731-01-18] NOTE 1 The coherence time is equal to coherence length divided by the phase velocity of light in a medium. NOTE 2 The coherence time is given approximately λ 0 2 /( c ⋅ ∆ λ ) where λ 0 is the central wavelength, ∆ λ is the spectral linewidth and c is the velocity of light in vacuum. [IEC 61931, definition 2.1.68] 3.1.23 well-cleaved well-cleaved end of fibre has a clean plane front perpendicular to the axis of the fibre 3.1.24 amplified spontaneous emission ASE optical power associated to spontaneously emitted photons amplified by an active medium in an optical amplifier [IEC 61931, definition 2.7.87] 3.1.25 directivity in a generic optical branching device, measure of the undesired transfer of a portion of optical power from one input port, when all other ports are optically matched for zero reflection [IEC 61931, definition 2.6.50] 3.1.26 central wavelength the average of those wavelengths at which the amplitude of a light source reaches or last falls to half of the maximum amplitude 3.1.27 spectral width measure of the wavelength range of a spectrum or spectral characteristic [IEV 731-06-24 modified] [IEC 61931, definition 2.7.42] 3.1.28 (stimulated) Brillouin scattering SBS non-linear scattering of optical radiation characterized by a frequency shift as for the Raman scattering, but accompanied by a lower frequency (acoustical) vibration of the medium lattice. The light is scattered backward with respect to the incident radiation NOTE In silica fibres the frequency shift is typically around 10 GHz. [IEC 61931, definition 2.1.88]