EFFECTS OF MECHANICAL-STRESS ON THE TRANSMISSION PROPERTIES OF OPTICAL-FIBER PACKAGED IN A COMPOSITE STRUCTURE

Optical circuit boards for system-level interconnection may be fabrica ted by bonding segments of optical fiber, in the configuration necessa ry for signal distribution, to a substrate such as a printed wiring bo ard. To measure the effects of mechanical stress on optical transmissi on, a four-point bend test is applied to prototype optical circuit boa rds. The results show that flexing a board to a strain of approximatel y 0.3% leads to a decrease in loss of 0.012 +/- 0.002 dB for multimode fiber. Flexing of a thin board, in two directions, around 40-in.- (10 1.6-cm-) bend-radius mandrels decreases fiber loss by almost 1 dB afte r 700 cycles. Single-mode fiber bonded to a board, however, exhibits a n increase in loss of 0.11 +/- 0.05 dB under an induced strain of 0.3% , a change that is not significant relative to typical loss-per-line b udgets in real systems.