Analyses of BER-referred noise-to-signal ratio in online measurements of high-baud-rate coherent receivers.

Digital coherent transmission features a very large transmission bandwidth and has played a main role in core optical transmission networks. With the progress of semiconductor technologies, practical coherent transceivers with rates over 100 Gbaud are becoming feasible. With such advances, the transceiver components must have lower power consumption and lower costs, and it becomes important to know how each component contributes to the overall transmission performance. Here, to decompose the effects of noise factors in high-baud-rate DP-16QAM transmissions, we used the theoretical relationship between the bit error rate (BER) and noise-to-signal ratio (NSR) and performed linear analyses. The NSR could be decomposed into individual noise contributions according to dependences on the inverse signal and local photocurrents. The obtained parameters were shown to be useful for predicting required optical signal-to-noise ratio (ROSNR) characteristics.

Wavelength selective switch array employing silica-based waveguide frontend with integrated polarization diversity optics.

We propose a waveguide frontend with integrated polarization diversity optics for a wavelength selective switch (WSS) array with a liquid crystal on silicon switching engine to simplify the free space optics configuration and the alignment process in optical modules. The polarization diversity function is realized by the integration of a waveguide-type polarization beam splitter and a polarization rotating half-wave plate in a beam launcher using silica-based planar lightwave circuit technology. We confirmed experimentally the feasibility of using our proposed waveguide frontend in a two-in-one 1 × 20 WSS. The experimental results show that the fabricated waveguide frontend provides a polarization diversity function without any degradation in optical performance.

Ultra-small, self-holding, optical gate switch using Ge2Sb2Te5 with a multi-mode Si waveguide.

We report a multi-mode interference-based optical gate switch using a Ge(2)Sb(2)Te(5) thin film with a diameter of only 1 µm. The switching operation was demonstrated by laser pulse irradiation. This switch had a very wide operating wavelength range of 100 nm at around 1575 nm, with an average extinction ratio of 12.6 dB. Repetitive switching over 2,000 irradiation cycles was also successfully demonstrated. In addition, self-holding characteristics were confirmed by observing the dynamic responses, and the rise and fall times were 130 ns and 400 ns, respectively.