Probability of modal noise in single-mode lightguide systems.

The probability of introducing modal noise in a single-mode lightguide system with a short length of fiber between high- loss splices is investigated. The cumulative probability of modal noise is useful for evaluating the risk involved in violating the recommended fiber minimum splicing length (the fiber length for zero probability of modal noise). The results show that for the current AT&T laser and fiber cutoff specifications (1330 nm maximum cutoff wavelength), the probability of encountering modal noise (a system power penalty exceeding 0.14 dB) is less than 0.6% for fiber lengths as short as three meters with splice losses of 0.5 dB.