10Gb/s SOA-EA modulator as colorless ONU for WDM-PON

• Description

  The use of a reflective SOA (RSOA) has been proposed several times to implement the Optical Network Unit (ONU) in WDM PONs. However, such elements have limited modulation bandwidth (typically 2.5 - 5 Gb/s). An alternative is to use an integrated structure formed by an SOA section and an electro-absorber section (EA) [1], which can operate at higher bit rates (10 - 40 Gb/s).
  In this application example (see Figure 1), the device is MQW-type, formed by one 200-µm-long SOA section with face reflection 1e-12 and a 100-µm-long EA section with one (high-reflection) HR face of 0.99. The SOA section is biased with a fixed current of 100 uA; the data signal is applied at the EA section with bias voltage swinging between -5 v (spaces) and 0 v (marks).

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• Typical Results

  Due to the properties of EA, the spectral response of the device strongly depends on the applied voltage. As a result, each ONU would transmit with a different power level and signal quality (Figure 2). The spectral properties of EA can be adjusted in order to homogenize the different WDM channels by adjusting the voltage dependency of the peak absorption and absorption bandwidth (Figure 3).
  Figure 4 shows the eye diagrams for the channels at 192.4 THz and 193.8 THz, representing the outermost channels of a 16-WDM-channel 100-GHz-spaced band. The extinction ratio is on the order of 30 dB and the difference in the mark levels of the two extreme channels is less than 1.5 dB.

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• Further Information

  Keywords: PICs, semiconductors, multisection device, electro-absorber, EAM, SOA
  
  Similar demonstrations are available in VPIComponentMaker Photonic Circuits and on the VPIphotonics Forum.
  
  [1] A.Garreau, J.Decobert , C. Kazmierski, M-C. Cuisin, J-G. Provost, H.Sillard, F.Blache, D.Carpentier, J.Landreau, P.Chanclou, "10Gbit/s Amplified Reflective Electroabsorption Modulator for Colourless Access Networks", IPRM 2006, paper TuA2.3.

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