This paper explores experimentally the impairments in performance that are generated when multiple single-sideband (SSB) subcarrier multiplexing (SCM) signals are closely allocated in frequency to establish a spectrally efficient wavelength division multiplexing (WDM) link. The performance of cost-effective SSB WDM/ SCM implementations, without optical filters in the transmitter, presents a strong dependency on the imperfect sideband suppression ratio that can be directly achieved with the electro-optical modulator. A direct detected broadband multichannel SCM link composed of a state-of-the-art optical IQ modulator and five quadrature phase-shift keyed (QPSK) subcarriers per optical channel is presented, showing that a suppression ratio of 20 dB obtained directly with the modulator produced a penalty of 2 dB in overall performance, due to interference between adjacent optical channels.
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Funding: Science Foundation Ireland (09/IN.1/12653, 10/CE/I1853); Enterprise Ireland (CFTD CF/2011/1627); and EPSRC (EP/L000091/1)
- optical IQ modulator
- sideband suppression ratio (SSR)
- subcarrier multiplexing (SCM)
- wavelength division multiplexing (WDM)