Optical transmitter / receivers for use in a DWDM systems are provided. Transmission of data signals in a quadrature-return-to-zero (QRZ) format achieves a
data transmission rate equal to eight times a base
data rate, i.e., 80 Gbps over a 100 GHz channel if the base
data rate is 10 Gbps, with high non-linear performance by setting the polarization state of the data bands such that non-linear effects induced by PMD are reduced. Additionally, a
transmitter achieves a transmission
data rate equal to 16 times the base data rate by
sharpening the QRZ pulses and
interleaving pulse-sharpened QRZ data signals in the
time domain, further doubling the data rate. Using counterpropagation in the
transmitter, carrier signals and data signals
traverse the same length of
fiber, reducing fringing effects in the
transmitter. Related techniques enhance reception and detection of data at high data rates. A local pulse-sharpened carrier is mixed with a QRZ
data signal at a
detector reducing amplification
noise by a factor of two. A bi-directional
Erbium-doped
fiber amplifier is used to amplify a
carrier signal while limiting fringing effects by sending carrier and data signals along equal
optical path lengths. Non-linear effects are reduced by transmitting carrier signals in an othogonal polarization state with respect to data signals, and PMD
phase noise effects are compensated for in both single channel and DWDM multi-channel systems by using
delay management.