A bi-directional WDM transmission link that changes the channel-count assigned in each direction is proposed for efficiently accommodating IP traffic which is characterized by directional volume asymmetry. A novel bi-directional optical amplifier is also proposed for overcoming the problems that arise in realizing the proposed link. The asymmetric, bi-directional, repeatered WDM transmission of 8 (total) 10 Gbit/s, 50 GHz-spaced channels over eleven 50 km spans is successfully demonstrated. The experimental results clarify that, owing to the use of the proposed bi-directional amplifier, directional asymmetry in channel-count and Rayleigh backscattering do not result in any significant performance degradation. Based upon an analysis of backscattering induced impairment, we show that the total transmission loss of 1000 dB can be supported if the span loss is 20 dB.

We clarify the effectiveness of receiver-side compensation in offsetting fiber Bragg grating (FBG) dispersion induced-electrical signal-to-noise ratio (SNR) degradation in a 10 Gb/s 8-channel wavelength-division multiplexing (WDM) 6,400 km transmission system. The receiver-side compensation greatly improves the SNR degradation. The allowable accumulated FBG dispersion is -400 1000ps/nm for the worst arrangement, a single FBG at the transmitter, which is about half the accumulated fiber dispersion permissible with receiver-side compensation.

This paper proposes a novel coefficient called Practical Gain" which determines how much cascaded laser amplifiers can extend the transmission length. It confirms that a high-speed transmission system needs laser amplifiers with high saturation power.