A Study on the Effect of Ultra-Wide Band WDM on Optical Transmission Systems

In the optical communication, ultra-wide band (UWB) wavelength division multiplexing (WDM) transmission systems have been gathering considerable attention because it is becoming rapidly difficult to increase capacity per optical fiber within conventional limited bandwidths. Our aim is to extend the wavelength for UWB WDM systems from the widely used C or L bands to additional bands such as the S, E, and O bands. For these wavelengths to be used in a practical manner, it is necessary to study how repeater configurations such as multiplexer and optical amplifiers and inter-channel interference caused by stimulated Raman scattering (SRS) will impact optical transmission systems. We study these problems through two UWB WDM experiments. In the first, we demonstrate the first ever 5-band WDM transmission and devise a format for allocating wavelength adaptive modulation to exhaustively use wavelength dependent optical signal-to-noise ratio (OSNR). The experiment setup includes 5 channel signals each allocated in each band and 5-band WDM repeater constructed of WDM coupler, 3-dB couplers, and four type of optical amplifiers. In the second, we investigate the inter-channel interference effect from SRS between 35-channel S- and 40-channel L-band 16QAM signal transmission over 210 km. The experimental results show that there is only optical power transition between S and L bands and that no nonlinear crosstalk interference is observed.