1、 TIA/EIASTANDARDFOTP-204Measurement of Bandwidth onMultimode FiberTIA/EIA-455-204DECEMBER 2000TELECOMMUNICATIONS INDUSTRY ASSOCIATIONThe Telecommunications Industry AssociationRepresents the Communications Sector of ANSI/TIA/EIA-455-204-2000Approved: December 19, 2000TIA/EIA-455-204Copyright Telecom
2、munications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NOTICETIA/EIA Engineering Standards and Publications are designed to serve the public interestthrough eliminating misunderstandings between manufa
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4、er ofTIA/EIA from manufacturing or selling products not conforming to such Standards andPublications, nor shall the existence of such Standards and Publications preclude their voluntaryuse by those other than TIA/EIA members, whether the standard is to be used either domesticallyor internationally.S
5、tandards and Publications are adopted by TIA/EIA in accordance with the American NationalStandards Institute (ANSI) patent policy. By such action, TIA/EIA does not assume any liabilityto any patent owner, nor does it assume any obligation whatever to parties adopting the Standardor Publication.This
6、Standard does not purport to address all safety problems associated with its use or allapplicable regulatory requirements. It is the responsibility of the user of this Standard toestablish appropriate safety and health practices and to determine the applicability of regulatorylimitations before its
7、use.(From Standards Proposal No. 4700, formulated under the cognizance of the TIA FO-6.6Subcommittee on Fibers and Materials.)Published byTELECOMMUNICATIONS INDUSTRY ASSOCIATION 2000Standards and Technology Department2500 Wilson BoulevardArlington, VA 22201PRICE: Please refer to current Catalog ofEI
8、A ELECTRONIC INDUSTRIES ALLIANCE STANDARDS and ENGINEERING PUBLICATIONS or call Global Engineering Documents, USA and Canada(1-800-854-7179) International (303-397-7956)All rights reservedPrinted in U.S.A.Copyright Telecommunications Industry Association Provided by IHS under license with EIANot for
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10、nt. For information, contact:Global Engineering Documents15 Inverness Way EastEnglewood, CO 80112-5704 or callU.S.A. and Canada 1-800-854-7179, International (303) 397-7956Copyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or network
11、ing permitted without license from IHS-,-,-Copyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TIA/EIA-455-204iFOTP-204Measurement of Bandwidth on Multimode FiberCONTENTSTitle Page1
12、. Introduction12. Applicable Documents 13. Apparatus 24. Sampling and Specimens .55. Procedure66. Calculations or Interpretation of Results .77. Documentation 88. Specification Information.9Annex A (Normative).10Annex B (Normative).13Annex C (Normative) 14Annex D - Informative .15Appendix A FOTP-541
13、7Copyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TIA/EIA-455-204iiCopyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reprod
14、uction or networking permitted without license from IHS-,-,-TIA/EIA-455-2041FOTP-204Measurement of Bandwidth on Multimode Fiber(From EIA Standards Proposal No. PN-7200 formulated under the cognizance of TIA FO-6.6,Subcommittee on Optical Fibers and Materials.)This FOTP Is part of the series of test
15、procedures included within Recommended StandardTIA/EIA-455.This is a consolidated FOTP for multi-mode fibre bandwidth measurement FOTPs 30 and 51.There are 4 annexes, 3 of them normative and 1 informative, and 1 informative appendixKey words: pulse distortion, frequency domain1. Introduction1.1 Scop
16、eThis document describes two methods for determining and measuring the informationtransmission capacity of TIA/EIA-4920000-B Class I (glass core) multi-mode optical fibers. Thebaseband frequency response is directly measured in the frequency domain by determining thefiber response to a sinusoidally
17、modulated light source. The baseband response can also bemeasured by observing the broadening of a narrow pulse of light. The two methods are:Method A Optical Time Domain Measurement Method (Pulse Distortion)Method B Frequency Domain Measurement MethodEach method can be performed using one of two la
18、unches: an overfilled launch (OFL) conditionor a restricted mode launch (RML) condition.Note: These test methods are commonly used in production and research facilities andare not easily accomplished in the field.1.2 Definition, Bandwidth ( -3 dB)The 3dB bandwidth of an optical fiber is defined as t
19、he lowest frequency where the magnitudeof the baseband frequency response in optical power has decreased by 3 dB relative to thepower at zero frequency. Various methods of reporting the results are described in theappendices, but the results shall be expressed in terms of the -3 dB (optical power) f
20、requencyunless otherwise specified by the Detail Specification.2. Applicable DocumentsTest or inspection requirements, definitions, and application guidelines may include, but are notlimited to, the following references:EIA/TIA-440-B Fiber Optic TerminologyCopyright Telecommunications Industry Assoc
21、iation Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TIA/EIA-455-2042FOTP-54 (EIA/TIA-455-54B) Mode Scrambler Requirements for Overfilled LaunchingConditions for Multimode FibersFOTP-57 (EIA/TIA-455-57A) Optical Fiber End Pre
22、paration and ExaminationTIA/EIA 4920000-B Generic specification for Optical FibersTSB-20 (TIA/EIA 62-20) The Use of RML and EF measurements for enhancingsystems performance13. Apparatus3.1 Radiation Source3.1.1 Optical Time Domain Measurement Method (pulse distortion measurement) (Method A) -Use a r
23、adiation source such as an injection laser diode that produces short duration, narrowspectral width pulses for the purposes of the measurement. The pulse distortion measurementmethod requires the capability to switch the energy of the light sources electrically, optically ormechanically.3.1.2 Freque
24、ncy Domain Measurement Method (Method B) - Use a radiation source such as acontinuous wave (CW) injection laser diode for the purposes of the measurement. Thefrequency domain measurement method requires the capability to modulate the energy of thelight sources electrically, optically or mechanically
25、.3.1.3 For both methods, use a radiation source with a center wavelength that is known andwithin 10 nm of the nominal specified wavelength. For injection laser diodes, laser emissioncoupled into the fiber must exceed spontaneous emission by a minimum of 15 dB (optical).3.1.4 For both methods, use a
26、source with sufficiently narrow linewidth to assure themeasured bandwidth is at least 90% of the intermodal bandwidth. This is accomplished bycalculating the Normalized Intermodal Dispersion Limit, NIDL (refer to Annex A).3.1.5 Calculate the Normalized Intermodal Dispersion Limit (NIDL, see Annex A.
27、) for eachmeasurement wavelength from the optical source spectral width for that wavelength as follows:NIDL = IDF/, in GHzkmwhere: is the source Full Width Half Maximum (FWHM) spectral width in nanometers,IDF is the Intramodal Dispersion Factor (GHzkmnm) from Annex A according to thewavelength of th
28、e source.NIDL is not defined for wavelengths from 1200 to 1400 nm. The source spectral width for thesewavelengths shall be less than or equal to 10 nm, FWHM.NOTE 1: The acceptability of an NIDL value depends upon the specific users testrequirements. For example, a 0.5 GHzkm NIDL would be satisfactor
29、y for checking that1The TSB has not been publishedCopyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TIA/EIA-455-2043fibers had minimum bandwidths greater than some value less than
30、 500 MHzkm, butwould not be satisfactory for checking that fibers had minimum bandwidths greater than500 MHzkm. If the NIDL is too low, a source with smaller spectral width is required.3.1.6 The radiation source shall be stable throughout the duration of a single pulse and overthe time during which
31、the measurement is made.3.2 Launch System3.2.1 Overfilled launch (OFL) - Use a mode scrambler between the light source and the testsample to produce a controlled launch irrespective of the radiation properties of the light source.The output of the Mode Scrambler shall be coupled to the input end of
32、the test sample inaccordance with FOTP-54. The fiber position shall be stable long enough to perform themeasurement. A viewing system may be used to aid fiber alignment where optical imaging isused.Provide means to remove cladding light from the test sample. Often the fiber coating is sufficientto p
33、erform this function. Otherwise, it will be necessary to use cladding mode strippers nearboth ends of the test sample. The fibers may be retained on the cladding mode strippers withsmall weights, but care must be taken to avoid microbending at these sites.3.2.2 Restricted mode launch (RML) - The RML
34、 for bandwidth measurement is created byfiltering the overfilled launch (as defined by FOTP-54) with a RML fiber. The OFL is defined byFOTP 54 and it needs to be only large enough to overfill the RML fiber both angularly andspatially per FOTP 54. The RML fiber has a core diameter of 23.5 m +/- 0.1 m
35、, and anumerical aperture of 0.208 +/- 0.01. The fiber must have a graded-index profile with an alphaof approximately 2 giving an OFL bandwidth greater than 700 MHz-km at both 850 and 1300nm. For convenience, the clad diameter should be 125 m. The RML fiber should be at least1.5 meters in length to
36、eliminate leaky modes; and it should be less than 5 meters in length toavoid transient loss effects. The launch exiting the RML fiber is then coupled into the fiber undertest (e.g. by butt coupling or using optics).Provide means to remove cladding light from the test sample. Often the fiber coating
37、is sufficient toperform this function. Otherwise, it will be necessary to use cladding mode strippers near bothends of the test sample. The fibers may be retained on the cladding mode strippers with smallweights, but care shall be taken to avoid microbending at these sites.(NOTE: In order to achieve
38、 the highest accuracy, tight tolerances are required on thegeometry and profile of the RML fiber. In order to achieve the highest measurementreproducibility, tight alignment tolerances (e.g. 0.5 m) are required in the connectionbetween the launch RML fiber and the fiber under test to insure the RML
39、fiber iscentered to the fiber under test.)3.3 Detection System3.3.1 The output optical detection apparatus shall be capable of coupling all guided modesfrom the test sample to the detector active area such that the detection sensitivity is notsignificantly mode-dependent. The detector shall respond
40、linearly over the range of powerdetected. An optical attenuator may be used to control the optical intensity on the detector.Copyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TIA/
41、EIA-455-20443.3.2 A device shall be available to position the specimen output end with sufficient stabilityand reproducibility to meet the conditions of 3.3.1.3.3.3 An optical detector shall be used that is suitable for use at the test wavelength, linear inamplitude response, spatially uniform to wi
42、thin 10%, and sufficiently large to detect all emittedpower.3.3.4 The detected optical signal shall be displayed on a suitable instrument, such as a highspeed, sampling oscilloscope with calibrated sweep rate for the time domain method and anelectrical spectrum analyzer for the frequency domain meas
43、urement. The detection electronicsas well as any signal preamplifier; shall be linear in amplitude response (nonlinearities less than5%) over the range of encountered signals.3.4 Recording System3.4.1 For the optical time domain method (Method A), use an oscilloscope suitably connectedto a recording
44、 device, such as a digital processor, to store the received pulse amplitude as afunction of time. For temporal measurements, data taken from the oscilloscope display shall beconsidered secondary to those derived from the recorded signal.3.4.2 For the frequency domain method (Method B), use a trackin
45、g generator-electricalspectrum analyzer combination or the equivalent to detect, display and record the amplitude of theRF modulation signal derived from the optical detector. This must be done in such a manner as toreduce harmonic distortion to less than 5%.3.5 Computational EquipmentFor the optica
46、l time domain method (Method A), computational equipment capable ofperforming Fourier transforms on the detected optical pulse waveforms as recorded by thewaveform recording system shall be used. This equipment may implement any of the severalFast Fourier Transforms or other suitable algorithms, and
47、 may be useful for other signalconditioning functions, waveform averaging and storage as well.3.6 Overall System PerformanceNOTE: This section provides a means of verifying system stability for the duration of ameasurement or the system calibration period, depending on the method used (A or B,see 5.
48、1 and 5.2, respectively).3.6.1 The measurement system stability is tested by comparing system input pulse Fouriertransforms (Method B) or input frequency responses (Method A) over a time interval. As shownin Annex B2, a bandwidth measurement normalizes the fiber output pulse transform by thesystem calibration transform. If a reference sample is substituted for the fiber sample, theresultant response, H(f), represents a comparison of the system to itself over the time interval.This normalized system amplitude stability is used to determine the System Stability FrequencyLimit (SSFL).3.6.2 Th
