ÿWPCL ûÿ2BJ|xÐ ` ÐÐÌÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿàH øÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÌÐÐ °°°è ÐÑ Âx„|ü@Ž ÑÐ Å@8Ø'@8Ø'Å Ð5.ÁàÁÁHÁÓÓÃÃRecommendation G.654ÄÄ Áà&ÁCHARACTERISTICS OF A 1500 nm WAVELENGTH LOSS©MINIMIZEDƒ Áà2ÁSINGLE©MODE OPTICAL FIBRE CABLEƒ ÁàÁÁHÁThe CCITT, ÃÃconsideringÄÄ Ð H ÐÁàÁÁHÁ(a)Á   Áthat very low loss fibres are required in some telecommunication network applications; ÁàÁÁHÁ(b)Á   Áthat the foreseen potential applications may require several kinds of single©mode fibres differing in: ÁàÁÁHÁ©Âà  Âgeometrical characteristics;ÆÆ ÁàÁÁHÁ©Âà  Âoperation wavelength;ÆÆ ÁàÁÁHÁ©Âà  Âattenuation dispersion and other optical characteristics;ÆÆ ÁàÁÁHÁ(c)Á   Áthat Recommendations on different kinds of single©mode fibres can be prepared when practical use studies have sufficiently progressed, ÃÃrecommendsÄÄ ÁàÁÁHÁa single©mode fibre which has the zero dispersion wavelength in the 1300 nm wavelength region which is loss minimized at a wavelength around 1550 nm and which is designed for use in this region. ÁàÁÁHÁThe geometrical, optical and transmission characteristics of this fibre are described below. ÁàÁÁHÁThe meaning of the terms used in this Recommendation are given in Annex A and the guidelines to be followed in the measurements to verify the various characteristics are indicated in Annex B. ÃÃNoteÄÄ © The characteristics of this fibre and the relevant values will be verified as studies and experience progress. 1.ÁàÁÁHÁÃÃFibre characteristicsÄÄ 1.1ÁHÁÁ  ÁÃÃMode field diameterÄÄ Ð à ÐÁàÁÁHÁThe nominal value of the mode field diameter at 1550 nm shall be xx ÀÀm. The mode field diameter deviation should not exceed the limits of ÀÀ 10% of the nominal value. ÃÃNoteÄÄ © The value for xx has to be specified. A value of 10.5 for xx is one possibility. 1.2ÁHÁÁ  ÁÃÃCladding diameterÄÄ ÁàÁÁHÁThe recommended nominal value of the cladding diameter is 125 ÀÀm. The cladding deviation should not exceed the limits of ÀÀ 2.4%* (ÀÀ 3 ÀÀm). 1.3ÁHÁÁ  ÁÃÃMode field concentricity errorÄÄ ÁàÁÁHÁThe recommended mode field concentricity error at 1550 nm should not exceed 1 ÀÀm*. 1.4ÁHÁÁ  ÁÃÃNon©circularityÄÄ 1.4.1ÁHÁÃÃMode field non©circulatoryÄÄ ÁàÁÁHÁIn practice, the mode field non©circularity of fibres having nominally circular mode fields is found to be sufficiently low that propagation and jointing are not affected. It is therefore not considered necessary to recommend a particular value for the mode field non©circularity. It is not normally necessary to measure the mode field non©circularity for acceptance purposes. 1.4.2ÁHÁÃÃCladding non©circularityÄÄ ÁàÁÁHÁThe cladding non©circularity should be less than 2%. For some particular jointing techniques and joint loss requirements, other tolerances may be appropriate. 1.5ÁHÁÁ  ÁÃÃCut©off wavelengthÄÄ ÁàÁÁHÁThe cut©off wavelength values shall be between xxxx nm and yyyy nm for À/Àc, and smaller than zzzz nm for À/Àcc. ÃÃNoteÄÄ © The values for xxxx, yyyy and zzzz have to be specified; values of 1350 for xxxx, 1600 for yyyy and 1530 for zzzz are one possibility. 1.6ÁHÁÁ  ÁÃÃ1550 nm bend loss performanceÄÄ ÁàÁÁHÁUnder study. ÃÃNoteÄÄ © The performance of this fibre should not be worse than fibre designed to meet Recommendation G.653. 1.7ÁHÁÁ  ÁÃÃMaterial properties of the fibreÄÄ ÁàÁÁHÁThis is given in section 1.7 of Recommendation G.652. 1.8ÁHÁÁ  ÁÃÃExample of fibre design guidelinesÄÄ ÁàÁÁHÁSupplement 33 gives an example of fibre design guidelines for matched cladding fibres used by one organization. ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ * Under study. 2.ÁàÁÁHÁÃÃFactory length specificationsÄÄ 2.1ÁHÁÁ  ÁÃÃAttenuation coefficientÄÄ ÁàÁÁHÁOptical fibre cables covered by this Recommendation shall have attenuation coefficients in the 1550 nm region* below 0.25 dB/km*. ÃÃNoteÄÄ © The lowest values depend on fabrication process, fibre composition and design, and cable design. Values of 0.15 to 0.20 dB/km in the 1550 nm region have been achieved. 2.2ÁHÁÁ  ÁÃÃChromatic dispersion coefficientÄÄ ÁàÁÁHÁThe maximum chromatic dispersion coefficient in the 1550 nm wavelength region of single©mode fibres covered in this Recommendation shall be 20 ps/(nmÃÃ.ÄÄkm). Ô w.ÔŒ3.ÁàÁÁHÁÃÃElementary cable sectionsÄÄ ÁàÁÁHÁAs given in ÀÀ 3 of Recommendation G.652. ÁàÀNÁANNEX Aƒ ÁàÀQÁƒ ÁàÀEÁ(to Recommendation G.654)ƒ ÁàÀQÁƒ ÁàÀ:ÁMEANING OF THE TERMS USED IN THE RECOMMENDATIONƒ ÁàÁÁHÁMost of the definitions contained in Annex A to Recommendation G.652 are in principle applicable also to loss©minimized fibre. Because of limited experience with this type of fibre, further study of the suitability of some definitions is needed. ÁàÀNÁANNEX Bƒ ÁàÀQÁƒ ÁàÀEÁ(to Recommendation G.653)ƒ ÁàÀQÁƒ ÁàÀ8ÁTEST METHODS FOR LOSS©MINIMIZED SINGLE©MODE FIBRESƒ ÁàÁÁHÁThe present experience on loss©minimized single©mode fibres is rather limited; therefore further study is needed on some reference and alternative test methods for this type of fibre. Nevertheless, most of the test methods described in Annex B to Recommendation G.652 are in principle applicable also to loss©minimized fibres. Therefore, for this annex, reference is made to the corresponding test methods of Annex B in Recommendation G.652; the specifics of each test procedure need further study. It should be noted that the working wavelength for G.654 fibres is in the 1550 nm region. ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ * Under study.