TIA-455-199-2002.pdf
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1、 TIA DOCUMENT FOTP-199 In-line Polarization Crosstalk Measurement Method for Polarization- Maintaining Optical Fibers, Components, and Systems TIA-455-199 DECEMBER 2002 TELECOMMUNICATIONS INDUSTRY ASSOCIATION The Telecommunications Industry Association represents the communications sector of Copyrig
2、ht Telecommunications Industry Association Provided by IHS under license with EIALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/29/2007 21:38:44 MDTNo reproduction or networking permitted without license from IHS -,-,- NOTICE TIA Engineering Standards and Publications are de
3、signed to serve the public interest 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 their particular need. The exi
4、stence of such Publications shall not in any respect preclude any member or non-member of TIA from manufacturing or selling products not conforming to such Publications. Neither shall the existence of such Documents preclude their voluntary use by non-TIA members, either domestically or internationa
5、lly. TIA DOCUMENTS TIA Documents contain information deemed to be of technical value to the industry, and are published at the request of the originating Committee without necessarily following the rigorous public review and resolution of comments which is a procedural part of the development of a A
6、merican National Standard (ANS). TIA documents shall be reviewed on a five year cycle by the formulating Committee and a decision made on whether to reaffirm, revise, withdraw, or proceed to develop an American National Standard on this subject. Suggestions for revision should be directed to: Standa
7、rds is the line-width of the light source at the 3 dB intensity level. Beat length. The length of fiber needed to create a 2 (360-degree) phase difference between orthogonal polarization states. It can be expressed by the following relation: BLB/= (2) where is the center wavelength of the source; B
8、is the birefringence of the fiber given as (ne no); ne is the extraordinary refractive index of the sample; no is the ordinary refractive index of the sample. h-parameter. A length normalized form of polarization crosstalk. The attribute h has units of inverse meters and is given by the equation ()
9、maxmin 1 /tanh/1PPLh = (3) where L is the fiber length; Pmax and Pmin are the portions of the optical power with polarization plane parallel and perpendicular, respectively, to the excited axis. The plane of polarization of the light launched into the fiber is parallel to either principal optical ax
10、is. The function tanh-1 is the inverse hyperbolic tangent. For Pmin/Pmax less than 0.1, a sufficient approximation to the above equation is ()LPPh/ maxmin = . (4) Copyright Telecommunications Industry Association Provided by IHS under license with EIALicensee=IHS Employees/1111111001, User=Wing, Ber
11、nie Not for Resale, 03/29/2007 21:38:44 MDTNo reproduction or networking permitted without license from IHS -,-,- 4 2 Normative references Test or inspection requirements may include, but are not limited to, the following references: FOTP-57 (EIA-455-57), Optical Fiber End Preparation and Examinatio
12、n FOTP-80 (EIA-455-80), Cutoff Wavelength of Uncabled Single-mode Fiber by Transmitted Power FOTP-193 (EIA-455-57), Polarization Crosstalk Method for Polarization- Maintaining Optical Fiber and Components Copyright Telecommunications Industry Association Provided by IHS under license with EIALicense
13、e=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/29/2007 21:38:44 MDTNo reproduction or networking permitted without license from IHS -,-,- 5 3 Apparatus Figure 1 provides an example of the use of this method to measure the polarization crosstalk along a section of PM fiber that is i
14、lluminated through a rotatable polarizer. In this case, light passes through a polarizer and is coupled by a lens into the sample. (Many other configurations of the optical launch are possible. For example, light may be coupled directly from a laser chip to the PM fiber). Figure 1 Simplified block d
15、iagram of the polarization crosstalk method. 3.1 Narrowband light source Use a single-line laser (DFB or external cavity) or other narrow-band source with wavelength appropriate to the fiber under test. The source must be sufficiently coherent to avoid depolarization of the light by the PM fiber und
16、er test. In order for this to be true, the coherence length must satisfy a constraint based on the beat length of the PM fiber. Most PM fibers have beat lengths on the order of a few millimeters. See Annex A for details of the source coherence length constraint. 3.2 Polarizer Provide a polarizer wit
17、h extinction ratio at least 20 dB better than the polarization crosstalk value to be measured. Rotatable polarizer Heat. or stretch PMF under test Polarization adjuster Narrowband light source Polarimeter Data trace Copyright Telecommunications Industry Association Provided by IHS under license with
18、 EIALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/29/2007 21:38:44 MDTNo reproduction or networking permitted without license from IHS -,-,- 6 3.3 Input optics Use an optical lens to couple linearly polarized light into the test fiber. The lens should be of the low-birefrin
19、gence (strain-free) type to avoid transforming the launch polarization state from linear to elliptical polarization. 3.4 Connector support fixture For Samples with connectorized fiber pigtails, provide a fixture to align the key of the test fiber connector with the pass axis of the polarizer. 3.5 Ou
20、tput optics Connect the output of the test fiber directly to the polarimeter, or couple via a lens if the polarimeter has an open beam input port. 3.6 Polarimeter Use a fast polarimeter with Poincar sphere display to measure and record the output state of polarization of the test fiber. The polarime
21、ter may be of any type that measures the Stokes parameters and displays the measured polarization on the Poincar sphere. The wavelength range of the polarimeter must include the wavelength produced by the light source. 3.7 Heating and stretching fixtures Stretching and heating should be gently appli
22、ed to avoid damage to the fiber and its coating and, in the case of stretching, to avoid locally bending the fiber, allowing light to couple between the driven and the non-driven polarization mode. If the fiber is mechanically gripped for stretching, the gripping process should maintain the fiber in
23、 a straight, unbent trajectory. If the fiber is heated, the heat source should deliver heat comparable to that of a common hair dryer set at low to medium heat. 4 Preparation of the sample 4.1 The connector key of the fiber under test shall be nominally aligned with one of the principal axes, typica
24、lly the slow axis. 4.2 Support the test fiber in some manner with essentially zero tension (typically less than 15 gm). Copyright Telecommunications Industry Association Provided by IHS under license with EIALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/29/2007 21:38:44 MDT
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