1、 TIA-455-127-A-2006 APPROVED: NOVEMBER 30, 2006 REAFFIRMED: OCTOBER 6, 2014 TIA-455-127-A November 2006FOTP- 127-A Basic Spectral Characterization of Laser Diodes NOTICE TIA Engineering Standards and Publications are designed to serve the public interest through eliminating misunderstandings between
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20、-127-A Spectral Characterization of Laser Diodes Contents FOREWORDIII 1 INTRODUCTION .1 2 NORMATIVE REFERENCES1 3 APPARATUS.2 4 SAMPLING AND SPECIMENS .2 5 PROCEDURE A 3 6 PROCEDURE B 4 7 CALCULATIONS OR INTERPRETATION OF RESULTS 6 8 DOCUMENTATION .14 9 SPECIFICATION INFORMATION.15 ANNEX A16 REFEREN
21、CES .17 TIA -455-127-A iiiFOTP-127-ASpectral Characterization of Laser Diodes Foreword Continuation of FOTP 127, Spectral Characterization of Multimode Laser Diodes. This FOTP is part of the series of test procedures included within Recommended Standard TIA/EIA-455. Key words: Optical Spectrum Laser
22、 Diode Spectral Width TIA -455-127-A 11 Introduction 1.1 Intent This test procedure defines and updates the methodology for measuring the center (mean) wavelength, peak wavelength and the spectral width (rms1) of multilongitudinal mode (MLM), multitransverse mode (MTM), and single mode (SM) semicond
23、uctor lasers using a dispersive spectrophotometric method or other suitable methods. For SM lasers, only center wavelength should be used and it should be noted that other spectral characteristics, such as Side Mode Suppression Ratio (SMSR), Stop Band (SB) for distributed feedback (DFB) lasers for e
24、xample, are not covered by this document. Other measures of spectral width for MM lasers are also retained from previous versions of this document. Recent studies on the measurement of the optical spectrum from various coherent sources into multimode fiber have highlighted issues with measurement re
25、peatbility due to speckle pattern variations and launch conditioning of the optical source into the multimode optical fiber. In addition, using multitransverse mode sources, such as some VCSELs, with singelmode optical fiber can lead to undersampling of the complete optical spectrum. 1.2 Hazards Thi
26、s procedure involves potentially hazardous operations as discussed in this section. During the measurement, a laser may emit non-visible light. Personnel are strongly cautioned never to look directly into the laser or any fiber optic cabling at any time. Although the optical output power is generall
27、y not very high, virtually all the power is concentrated into a narrow frequency band, which implies that the energy can be focused into a very intense spot on the retina by the lens within the viewers eyes. For a complete review of laser safety guidelines, the reader is referred to the internationa
28、l standard IEC 60825-2. 2 Normative references Test or inspection requirements may include, but are not limited to, the following references: EIA/TIA-455-A, Standard test procedures for fiber optic fibers, cables, transducers, sensors, connecting and terminating devices, and other fiber optic. 1rms
29、refers to the standard deviation (1) of a distribution TIA -455-127-A 23 Apparatus The following apparatus and equipment is required to perform this test: 3.1 Optical spectrum analyzer Use a calibrated optical spectrum analyzer (OSA) following IEC/PAS 62129: This test equipment uses a dispersion spe
30、ctrophotometric method to resolve different wavelength components in the optical output of laser diodes. The various wavelength components are displayed by the OSA. Averaging the readings from the OSA will greatly increase the repeatability of the measurement. 3.2 Power supplies Use electrical power
31、 to operate the laser diode, which may include both continuous wave (CW) and modulated operating conditions. 3.3 Fiber cabling The OSA may support either or both SM and multimode (MM) fiber cabling as the optical source input. Use fiber jumper cabling between the optical source and the OSA utilizing
32、 either SM or MM cabling consistent with the optical source and OSA. The choice of fiber cabling can greatly influence the measured optical spectrum. In many cases, the optical fiber is the entrance aperature to the measurement system. For multitransverse mode lasers, the use of single mode optical
33、fiber is not recommended. When using multimode optical fiber, the user should be aware that the launch profile of the optical source into the optical fiber can effect the measured optical spectrum. In addition, coherent effects from the source and fiber interaction such as speckle can influence the
34、measurement repeatability. It is recommended that a fiber shaker as described in TIA/EIA-455-203 (FOTP-203) be employed in the measurement to mitigate these unwanted effects. 4 Sampling and specimens This document applies to all MLM , MTM and SM lasers. It therefore includes, but is not limited to,
35、Vertical Cavity Surface Emitting Lasers (VCSELs), Fabry-Perot (FP)lasers, distributed feedback (DFB) lasers, and distributed Bragg reflector (DBR) lasers. The detailed spectral characterization of single mode sources is beyond the scope of this FOTP. The test sample may consist of one of the followi
36、ng: (1) a laser chip with an arrangement to couple light into the OSA, or (2) a laser having a pigtailed optical connector, or TIA -455-127-A 3(3) a connectorized laser diode assembly, or (4) a laser diode with means to couple light into a fiber optic cable, or (5) a piece of equipment containing an
37、y of the above. In the case of MTM or MLM sources, care must be taken to eliminate any modal selectivity in the collection optics. An example of this is spatial filtering of the laser emission due to the low acceptance numerical aperture of the optical fiber or other lensing in the light collection
38、optics. In the case of low power laser diodes, care should be taken to avoid ambient light from affecting the measurement. Optical backreflections from connectors, splices, and test equipment may affect the emitted and measured optical spectrum. Care should be taken to minimize any backreflections f
39、rom the optical system to the laser. If a certain reflection level is specified by a relevant standard, then backreflections should be controlled as specified. 5 Procedure A Procedure A is more applicable to MTM laser diodes such as VCSELs. No simple test methodology will accurately measure the spec
40、tral width of an unmodulated SM source such as a DFB laser, or SM VCSEL sources, and the methodology presented herein will only provide the user with meaningful results for the center wavelength. For resolving the spectral width of SM lasers, use either a Fabry-Perot etalon, heterodyne, or homodynin
41、g techniques. These measurement techniques are beyond the scope of this FOTP, and more information can be found in the cited references. Some modulated SM sources may yield acceptable measurements using procedure A. 5.1 With the exception of ambient temperature, the standard ambient conditions of EI
42、A/TIA 455-A shall be used, unless otherwise specified. The ambient or reference point temperature shall be 23C 2C, unless otherwise specified. 5.2 Turn on the OSA and allow the recommended warm up and settling time to achieve the rated measurement level. 5.3 Unless otherwise specified, apply an inpu
43、t electrical signal to modulate the light output at the maximum rated frequency or using communication standard specified test patterns. If the measurement is to be done under DC conditions, apply the desired current. Allow sufficient time (per manufacturers TIA -455-127-A 4recommendations or as spe
44、cified in the detail specifications) for the laser transmitter assembly to reach a steady state temperature. 5.4 Connect the optical output of the laser under test to the optical input of the OSA. 5.5 Adjust the OSA controls as follows 5.5.1 Set the OSA wavelength step size (resolution) in order to
45、adequately sample/resolve any spectral detail in the optical spectrum of the laser under test. The OSA resolution bandwidth (RBW) should then be selected as at least two times the step size in the frequency domain (Hz) in order to comply to the Nyquist criterion. (A good rule of thumb is to have at
46、least 4 measurement points in the first 3dB to define each peak) 5.5.2 Set the OSA wavelength range in order to adequately incorporate all of the detectable modes. 5.5.3 Using the gain and reference level control, set an appropriate gain of the signal such that the peak mode extends over the vertica
47、l scale. 5.5.4 It is important to adjust the scanning time, the resolution bandwidth, and the video bandwidth (if implemented in the OSA) to obtain an adequate signal to noise ratio, generally with a noise floor at least 30dB below the maximum power reading. 5.6 If available, use a log scale for the
48、 amplitude measurement to achieve the maximum dynamic range. 5.7 If available, use signal averaging of at least 10 optical spectrum measurements to obtain a stable reading. The addition of signal averaging will significantly improve the measuement repeatability. To mitigate effects of laser speckle
49、in multimode fiber, it is further recommended that a fiber shaker as described in TIA/EIA-455-203 (FOTP-203) be employeed in the measurement. 5.8 For OSAs that are not capable of performing the calculation internally, download the measured optical spectra data to a computer for further analysis in a format that contains both the wavelength and amplitude of all points in the measurement. 6 Procedure B 6.1 With the exception of ambient temperature, the standard ambient conditions of EIA/TIA-455-A shall be used, unless otherwise specified. The ambient or reference point temperatu
