Exploitable results
The synQPSK project has yielded commercially available components (QPSK modulator, 90° hybrid, 90° hybrid with photoreceiver), pre-commercial research samples (SiGe 10-Gs/s-ADCs, CMOS signal processing chip, evaluation boards for these), the worldwide first realtime synchronous QPSK transmission with DFB lasers, the worldwide first realtime polarizationmultiplexed synchronous QPSK transmission and electronic polarization control, also with DFB lasers, the (until now) worldwide fastest experimental demonstration of electronic polarization control (40 krad/s) and the worldwide second (after Nortel) set of synQPSK ASICs (SiGe, CMOS). Regarding LiNbO3 components (QPSK modulators, 90° hybrids) expectations have been fully reached. Regarding InP photoreceivers there is presently a yield problem, still caused by a photoresist supplier. All the same CIL trusts UDE and intends to go into a commercial venture with them. Regarding SiGe ADCs, UPb has not fully reached the desired sampling frequency and accuracy. Reasons for this are known and can be overcome.
regarding CMOS signal processing, Upb has reached individual demultiplexer performance to a good degree, and full-custom CMOS signal processing at full speed, but their joint execution is limited by suboptimal chip mounting. Beyond that, Upb has found an algorithm that allows transmitting synchronous 16-QAM and similar schemes also with standard DFB lasers, in contrast to current international efforts where external-cavity lasers are used. Upb has also extended its electronic polarization control for PMD compensation. In addition to the commercial success of Photline and CIL, Upb has won national research contracts for further investigation into synchronous QPSK transmission, has won an international contract for ADC delivery and is about to sign a contract for further ADC development. All have contributed to about 9 invited and a number of regular conference and journal publications as well as press releases with international reach.
most partners have gathered in an - unfortunately declined - follow-up proposal 'synQAM' with the targets of 100 GbE transmission and 16-QAM transmission with DFB lasers. We believe the project goals set up there continue to be valid and will try to submit another similar proposal in the future. Many of the mentioned possible improvements are also being undertaken, as far as resources permit, at own initiative and funded by national and international partners. The strategic impact of the synQPSK project is that the results allow for synchronous QPSK transmission with standard DFB lasers for the first time. This breakthrough will enable the widespread use of synchronous RZ-QPSK transmission with polarization division multiplex. The value of this scheme lies in avoiding the large chromatic and polarization mode dispersion penalties of 40 Gbit/s systems due to the reduced symbol rate of only 10 Gsymbols/s. Also, the RZ signal format together with PSK guarantees a superb resilience against nonlinear degradations due to cross phase modulation. The combination of QPSK and polarization division multiplex means that the cost per bit is lower than for binary PSK or for the transmission of only one polarization because the receiver complexity stays essentially unchanged. For the new 100 Gbit/s Ethernet standard, the demonstrated feasiblity of QPSK with polarization multiplex is an important milestone and is expected to continue to play an important role in the ongoing discussion.
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