1、 TIA/EIA STANDARD FOTP-203 Launched Power Distribution Measurement Procedure for Graded-Index Multimode Fiber Transmitters TIA/EIA-455-203 JUNE 2001 TELECOMMUNICATIONS INDUSTRY ASSOCIATION The Telecommunications Industry Association Represents the Communications Sector of ANSI/TIA/EIA-455-203-2001 A
2、pproved: June 5, 2001 TIA/EIA-455-203 Copyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NOTICE TIA/EIA Engineering Standards and Publications are designed to serve the public inte
3、rest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standards and Publicat
4、ions shall not in any respect preclude any member or nonmember of TIA/EIA from manufacturing or selling products not conforming to such Standards and Publications, nor shall the existence of such Standards and Publications preclude their voluntary use by those other than TIA/EIA members, whether the
5、 standard is to be used either domestically or internationally. Standards and Publications are adopted by TIA/EIA in accordance with the American National Standards Institute (ANSI) patent policy. By such action, TIA/EIA does not assume any liability to any patent owner, nor does it assume any oblig
6、ation whatever to parties adopting the Standard or Publication. This Standard does not purport to address all safety problems associated with its use or all applicable regulatory requirements. It is the responsibility of the user of this Standard to establish appropriate safety and health practices
7、and to determine the applicability of regulatory limitations before its use. (From Standards Proposal No. 4669-A, formulated under the cognizance of the TIA FO-2.3 Subcommittee on Opto-Electronic Sources, Detectors this excludesfor instance lead sulphide vidicon detectors. Detectors must meet the de
8、tectorCopyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TIA/EIA-455-2032requirements of TIA/EIA-455-43 FOTP43. Absolute radiometric measurementof flux (optical power flow) is not
9、required. A computer is required to perform theneeded computations, which are too extensive to be performed manually.Although the present FOTP assumes a CCD camera, mechanically-scannedslitscan and pinhole cameras may also be used.Safety. All procedures in which an LED or laser source is used as the
10、 opticalsource shall be carried out using safety precautions in accordance with ANSIZ136.2, ANSI Z136.2.2 Normative referencesTest or inspection requirements may include, but are not limited to, the followingreferences:ANSI Z136.2 ANSI Z136.2, American National Standard for the safe use ofoptical fi
11、ber communication systems utilizing laser diode and LED sourcesFOTP-43 TIA/EIA-455-43, Output Near-Field Radiation Pattern Measurementof Optical Waveguide Fibers, December 1984.FOTP-54 EIA/TIA-455-54A, Mode Scrambler Requirements of OverfilledLaunching Conditions to Multimode Fibers, November 1990.F
12、OTP-58 EIA/TIA-455-58A, Core Diameter Measurement of Graded-IndexOptical Fibers, November 1990.FOTP-176 EIA/TIA-455-176, Method for Measuring Optical Fiber Cross-Sectional Geometry by Automated Gray-Scale Analysis, June 1993.Note: Non-normative references are listed in Annex A.7 Bibliography.3 Appar
13、atusAs the objective of the present FOTP is to optically characterize laser sources,many different laser sources will be used, while the rest of the apparatus is heldconstant. The apparatus is calibrated using a broadband incoherent calibrationsource (such as a LED or a xenon arc lamp) in place of t
14、he lasers.Figure 1 gives an overview of the apparatus used to perform thesemeasurements.Copyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TIA/EIA-455-20333.1 SourcesThere are two
15、kinds of source used in the present FOTP, the incoherentbroadband overfilled source used for calibration, and the various laser sourcesbeing tested, as described in the following paragraphs.There is always an optical connector between the source and the test jumperassembly.3.1.1 Calibration SourceTh
16、e purposes of the calibration source are to find the optical center of the testjumper assembly, and also to determine the geometric corrections needed toconvert 2D nearfield measurements taken in camera (TV) coordinates into theequivalent true geometric measurements, compensating for non-square pixe
17、ls,Optical PathSourcesOptical Connection between the sources and the test jumper assemblyFigure 1 Overview of ApparatusTest JumperAssemblyFiberShakerFiber end is movedin XYZ by theMicropositioner(not shown)Raw ImageDataCameraControlMicroscopeObjectiveOptional neutraldensity filterDetectorXYOpticalAx
18、isYXZSource ControlLedSourceLaser#1Laser#2Laser#NDetectorElectronicsControlComputer(Optional)Copyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TIA/EIA-455-2034imprecisely known ma
19、gnification factors, and the like. For these purposes, anincoherent broadband source which overfills the modes of the test jumperassembly is used in place of the laser sources under test.Any spectrally broad non-coherent light source, such as a tungsten-halogenlamp, a xenon arc lamp, or a light-emit
20、ting diode (LED) may be used to overfillthe test jumper assemblys fiber. The chosen calibration source shall be stablein intensity over a time period sufficient to perform the measurements.Optionally, a EIA/TIA-455-54A FOTP-54 mode scrambler may be used with thechosen calibration source to ensure mo
21、re uniform overfilling of the fiber.3.1.2 Laser Under TestThe only requirements on the lasers under test are that they have an operatingwavelength compatible with the test jumper assembly and the detector, and haveoptical connectors or splices compatible with those of the test jumper assembly.The co
22、nstruction details of the laser sources are otherwise unspecified.The laser drive current shall be sufficient to ensure that the laser always acts asa laser, rather than an LED.3.2 Test Jumper AssemblyThe purpose of the test jumper assembly is to strip cladding modes, and to allowspeckle to be avera
23、ged out by mechanical flexing of a portion of the test jumperassembly.The test jumper assembly shall be at least ten meters in length, made ofgermanium-doped near-parabolic graded-index fused-silica multimode glassClass Ia fiber with a core diameter of either 50 microns or 62.5 microns, and anoveral
24、l glass diameter of 125 microns. The test jumper assembly shall consist ofa single, uncut length of fiber with connectors at each end. The test jumperassembly connectors shall have single-mode mechanical tolerances, eventhough the fiber is multimode.3.3 Fiber ShakerThe purpose of the fiber shaker is
25、 to ensure that optical speckle is averaged out,with only a few percent of residual ripple or noise due to speckle being allowed toremain in the measured nearfields. Manual shaking of the fiber is generally notsufficient.Part of the test jumper assembly shall be mechanically shaken continuously inea
26、ch of three nominally orthogonal directions (using three independent shakermechanisms) during the measurement, making at least one hundred shakeCopyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without licens
27、e from IHS-,-,-TIA/EIA-455-2035cycles in each of the three directions during the measurement period. Theshake frequencies in the three directions shall be chosen such that the threeshake cycles synchronize no more often than once every five hundred cycles ofthe middle shake frequency.A fiber shaker
28、mechanism may be of any design as long as it induces largeamplitude movements and flexing in the optical fiber. Fiber transversedisplacements of more than 25 millimeters are suggested. The fiber shakersshall include a fiber holding fixture for securely holding the fiber.One exemplary mechanism, show
29、n in Figure 2, has three turns of fiber coiledinto a 3-ply figure-eight arrangement, with the loops each being approximately120 millimeters in diameter. A motor-driven eccentric drives a slider back andforth at about one stroke per second, alternately flattening and stretching oneloop of the figure
30、eight with 25-mm amplitude. Three such mechanisms in serieswill consume about 3*3*(2*0.120)= 6.8 meters of the test jumper assemblysfiber.FiberOutElasticFiberClampElastic FiberClamp120MMDIAMETERCIRCLE25mm peakDisplacementFigure 2 Fiber Shaker ExampleNotes:1) Only one figure-eight loop of the threeis
31、 shown here, for visual clarity. Use loose fiber clips as needed to keepfiber in place, in addition to elastic fiberclamps that prevent transmission of fiber motion. Loose fiber clips not shown.FiberIn2) Fiber is moved back and forth asshown, with a peak-to-peak amplitudeof about 25 millimeters, dis
32、torting onefiber loop.120MMDIAMETERCIRCLE120 mmDiameterCircle120 mmDiameterCircleCopyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TIA/EIA-455-2036Note: The fiber ends leading int
33、o and out of the fiber shakers must bemechanically fixed or stabilized to prevent movement of fibers at connectionpoints. In addition, the fiber shakers must be mechanically isolated from the restof the test setup so that vibrations are not transmitted to connection pointsthroughout the apparatus, o
34、r to the micropositioner, camera, or microscopeobjective. Vibration reduction is easier if the fiber shaker is both statically anddynamically balanced, and if all moving components are light in weight.Note: There is no required relation between the measurement period (containingthe one hundred strok
35、es) and the duration of a CCD camera exposure. Typically,in each measurement period, many exposures are taken and later summed, toavoid saturation of the CCD, and to ensure that speckle is in fact averaged outToo short a total exposure time will prevent the desired averaging out of speckle.3.4 Micro
36、positionerThe purpose of the Micropositioner is to bring the projected image of the fiberface into focus on the CCD chip within the camera, and also to supportgeometric calibration of the apparatus by making calibrated moves in X and Y,these axes being perpendicular to the optic axis Z.The X-axis an
37、d Y-axis accuracy and resolution shall be one micron or less(finer), and it shall be possible to sweep the centroid of the calibration-sourcenearfield image from one edge of the CCD chip to the other, in both X and Ydirections, by adjustment of the X and Y axes alone, with the nearfield imageremaini
38、ng substantially in focus on the CCD chip. The X-axis and Y-axisrepeatability error shall be no larger than one third of a micron. It shall bepossible to mechanically lock both the X and Y axes, to prevent drift in theapparent location of the test jumper assemblys optical center as tests areperforme
39、d.The Z-axis accuracy, repeatability, and resolution are unspecified, but shall besufficient to bring the system into focus, and it shall be possible to mechanicallylock the Z axis once focus is achieved, to prevent drift in the systemmagnification as tests are performed.3.5 Microscope ObjectiveSuit
40、able optics shall be provided which project the magnified image of the outputend of the test jumper assembly onto the receiving CCD chip such that the CCDcan measure the entire nearfield flux distribution. These optics shall not restrictthe numerical aperture of the formed image. (Based on EIA/TIA-4
41、55-43 FOTP-43. )Note: The actual magnification of the microscope objective as used in thepresent apparatus generally will not be the same as the nominal magnificationCopyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking pe
42、rmitted without license from IHS-,-,-TIA/EIA-455-2037factor engraved into the side of the objective, because the present apparatusdiffers from the standard microscope for which that nominal magnification factorwas computed.3.6 DetectorThe flux detectors shall be both linear and memoryless; this excl
43、udes forinstance lead sulphide vidicon detectors. Detectors shall satisfy the detectorrequirements of EIA/TIA-455-43 FOTP-43. Absolute radiometric measurementof flux (optical power flow) is not required.Automatic Gain Control (AGC), if present, shall be disabled.In CCDs with anti-blooming provisions
44、, saturation is considered to occur at thewhite-clip level, not ultimate saturation, to preserve linearity of response.If more than one in one thousand of the CCDs pixels are bad, or if the camerasoffsets and pixel crosstalk are too large to allow accurate measurements, replacethe camera. See Camera
45、 Optical Calibration in Section 5 for details.Note: Detector saturation may often be avoided by taking a number of very shortexposures and summing them pixel for pixel.Note: Neutral-Density (ND) filters, optionally used to prevent detector saturation,are most conveniently placed between the microsco
46、pe objective and thedetector, and should be slightly tilted (by a few degrees of angle) to preventreflections from the filter from reaching the source.4 Sampling and specimensLaser sources to be tested shall be chosen and prepared as defined by the userof the present FOTP, who shall document the sam
47、pling and preparationprocedures used, as described in Section 7 of the present FOTP. See Section 3for technical requirements on sources.5 ProcedureCopyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without lic
48、ense from IHS-,-,-TIA/EIA-455-20385.1 Overview of the Measurement ProcedureThis procedure consists of the following steps: 1) calibrate the camera, 2)measure the calibration sources 2D nearfield flux distribution, 3) measure one ormore laser launch 2D nearfield flux distributions, 4) perform the cal
49、culations, and5) report the results. Note that calibration of the apparatus is critical to theaccuracy of this measurement procedure. (See Annex A.5 for description of thekinds of noise and errors which calibration can correct.) There is one calibrationprocedure and one nearfield measurement procedure, each being used multipletimes. The following paragraphs first describe these two basic procedures, a
