Dither-free, accurate, and robust phase offset monitor and control method for optical DQPSK demodulator

Technologies for 40 Gb/s and 100Gb/s transmission

“…We understand RZ-DQPSK modulation scheme, having s a compact modulation spectrum and relatively wide PMD tolerance, has long been evaluated [2], and is already well established and proved technology [3], and is a promising solution. We studied and compared the various effects and influences and developed RZ-DQPSK transceivers [4,5]. In the actual presentation I will describe in some more detail.…”

Free-space optical delay interferometer with tunable delay and phase

“…Phase monitoring with a fixed time delay has been intensively discussed based on RF power monitoring [14] or based on a correlation method [15]. Although the efficiency of both methods has been demonstrated, the techniques are complicated, and they are limited to certain data formats and bitrates.…”

Stabilization of a delay interferometer for variable bit-rate DPSK receiver from 40 Gbit/s up to 160 Gbit/s

“…For the DPSK receiver, phase stabilization of the operational point of the DI is indispensable. Several techniques for the stabilization have been proposed and demonstrated [1][2][3][4][5][6]. In this paper, we present a stabilization scheme of the DI for DPSK optical receiver using a wavelength tunable continuous wave (CW) laser.…”