Optical performance monitoring (OPM) is considered as an important tool in order to operate and manage dynamic, flexible, and thus complex photonic networks. In this paper, firstly we review recent studies on OPM and discuss its possible applications, such as failure diagnosis of transmitter, receiver, and other transport equipment, optimization of system reach design, and so on. We then present two different types of in-band OSNR monitor, consisting of an optical bandpass filter, a photo-detector, and a signal processer. Since the proposed monitor might be realized by the same hardware implementation as an optical channel monitor (OCM), this is potentially integrated with an OCM in a low-cost fashion. We also explain a BER monitor, which is realized by the same hardware configuration as the above in-band OSNR monitor. The BER in the method is estimated by monitoring OSNR including nonlinear noise as noise source and taking the imperfection of Tx, Rx, and other equipment into account. Finally we develop FPGA-based optical performance monitor prototype and experimentally demonstrate successful monitoring performance.
Capacity demand has continued to increase exponentially. For the system capacity expansion, increasing the spectral
efficiency by using multi-level modulation formats may be a good candidate. One drawback of multi-level formats is the
requirement of higher signal-to-noise ratio. This requests more frequent OEO regenerations due to its shorter reach.
Optical regeneration using phase sensitive amplifier (PSA) has a possibility to prolong the reach by suppressing phase
noise generated through fiber transmission. In this paper, we discuss a network architecture having optical restoration
process, and its advantages and merits. Then, we show proposed PSA and optical restoration schemes and their system
tolerance against chromatic dispersion.