Conference Report: SYMPOSIUM ON OPTICAL FIBER MEASUREMENTS Boulder, CO September 15–17, 1992

The seventh Symposium on Optical Fiber Measurements was held on September 15-17, 1992 at NIST in Boulder, CO. Over 220 people attended the two and a half day meeting and heard a program consisting of 11 invited and 43 contributed papers with over half the papers coming from outside the United States. In addition, 10 committees associated with standards organizations like the Telecommunication Industry Association (TIA) and International Electrotechnical Commission (lEC) met in conjunction with the Symposium. The meeting covered metrology aspects of lightwave communications. While optical fiber measurements were emphasized, other lightwave components were also addressed including sources, detectors, integrated optic advices, passive filters, splitters, and connectors. The meeting scope covered metrology in both laboratory and field environments. Important technical topics of the meeting included optical time domain reflectometry (OTDR), single-mode fiber geometry, polarization effects in fiber, and optical fiber amplifiers. OTDRs have unique measurement capabilities and represent the largest market segment of fiber optic test equipment. They therefore continue to be a topic of interest at the Symposia. T. Horiguchi and other workers from Nippon Telegraph and Telephone (NTT) reported on an OTDR operating at 1600 nm. Usual OTDRs operate at typical system wavelengths of either 1300 or 1550 nm. By operating at longer wavelengths, where single-mode fiber bending loss is higher, the new OTDR has improved sensitivity for locating potential faults caused by excessive bending. Operation at 1600 nm is accomplished by using a Q-switched erbium fiber laser to pump a fiber Raman laser. A dynamic range of 24.5 dB is achieved with a resolution of 20 m. Future fiber networks may contain several fiber splitters for distribution. F. Kapron and J. Berardinelli from Bellcore described an algorithm for determining branch fault loss and reflectance when the OTDR "looks" through a splitter. To better quantify OTDR signatures, A. Judy from AT&T Bell Laboratories developed an expression which relates fiber backscatter and reflectance. J. Clayton and others from AT&T Bell Laboratories performed statistical analysis to determine the limitations of OTDRs when predicting fiber uniformity. Low coherence reflectometry is closely related in function to OTDR. It is an interferometric technique for obtaining very high resolution on short lengths of fiber. K. Takada from NTT reviewed the method in an invited paper. W. Sorin and D. Baney of Hewlett Packard described a method for improving the accuracy of reflectance measurements in the presence of fiber chromatic dispersion.