Therefore, the
use of optical buffers as a contention resolution technique in the OBS networks is
less than feasible. Nevertheless, several proposals, and many research activities, were
dedicated to the study of buffering techniques in OBS networks. Buffering is to delay
or to queue contending bursts instead of dropping them. If optical-electrical-optical
conversion is allowed (i.e., not an all-optical network) then random access electronic
buffers can be used to buffer the burst for a long time. However, to implement an
all-optical network (i.e., the data is maintained in the optical domain end-to-end), an
optical buffering technique is needed. Optical buffering currently can only be implemented
using Fiber Delay Lines (FDLs). The time that the bursts can be delayed is
directly proportional to the length of the FDL. More efficient optical buffers can be
realized through multiple delay lines of the same or different lengths, deployed in
stages (Chlamtac, Fumagalli, Kazovsky, Melman, et al., 1996) or in parallel (Haas,
1993). Such buffers can hold DBs for variable amounts of time. Recently, designs of
large optical buffers (Hunter, Cornwell, Gilfedder, et al., 1998; Tancevski, Castanon,
Callegati, & Tamil, 1999) were proposed without large delay lines.
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