Abstract
The deployment rate of wavelength division multiplexed passive optical networks (WDM-PONs) is expected to
accelerate with the availability of cost-efficient wavelength-specific transmitters. Fueled by this promise, we
propose and experimentally demonstrate a novel scheme that facilitates the use of reflective semiconductor optical
amplifiers (RSOAs) as colorless upstream transmitters. Central to the scheme is the use of a passive reflective path
that is placed at the remote node (RN) to reflect a spectral slice of the broadband amplified spontaneous emission
(ASE) light emitted from each RSOA. The reflected spectral slice, termed as a seeding light, establishes a
self-seeding of the RSOA with measurements indicating the self-seeded output to be incoherent with a low relative
intensity noise. The subsequent direct modulation of the self-seeding RSOA with nonreturn-to-zero data at 1.25 Gb/s
for upstream transmission exhibits good transmission and crosstalk performance after traversing 21 km of single-mode
fiber. Our proposed scheme eliminates the need for centralized broadband sources, external modulators, and active
temperature control within the RN and between the RN and the optical network unit. Aside from the feasibility study
of self-seeding RSOAs, we investigate the upstream performance dependence on the characteristics of the seeding
light. Our investigations reveal that there exists a noise floor limit of the bit error rate (BER) of the
self-seeded upstream signal. The noise floor is shown to vary with an initial optical seeding power that affects the
level of ASE noise suppression of the self-seeded upstream signal. Nonetheless, the RSOA self-seeds at a
user-defined wavelength with a sufficient suppression of ASE noise to achieve a BER=10<sup>-9</sup> with only -30.5 dBm of
initial optical seeding power. Our characterization of the frequency response of the RSOA reveals a high-pass filter
response that suppresses the modulation on the reflected seeding light, and thus stabilizing the self-seeded output.
Collectively, these features highlight the potential of using the self-seeding RSOAs to realize a cost-efficient
WDM-PON solution in the near future.
© 2007 IEEE
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