SEPTEMBER 20, 2007 -- At the European Conference and Exhibition on Optical Communication (ECOC) held this week in Berlin, Germany, Alcatel-Lucent (search for Alcatel-Lucent) delivered several post-deadline papers touting breakthroughs in optical network technology. Alcatel-Lucent Bell Labs and R&I researchers reported the successful demonstration of new advances in optical transmission with novel integrated optoelectronics sources and receiver. Alcatel-Lucent researchers also delivered three post-deadline papers that bring the company closer to 100-Gigabit Ethernet (search for 100-GbE) transmission.
Integrated optoelectronics sources and receiver
On the receiver side, Alcatel-Lucent researchers in Bell Labs' Crawford Hill, NJ facility demonstrated a novel compact optoelectronic receiver for differential quadrature phase-shift keying (search for DQPSK) reception that may ultimately contribute to reducing the cost and size of high-data-rate advanced-modulation-format optical transceivers, say Alcatel-Lucent representatives. In contrast to the current generation of receiver technologies where multiple components must be connected together with precise path lengths in order to support advanced modulations formats, this technology integrates an optical demodulator and four photodiodes on a single 3.2 mm x 0.8 mm InP-based chip. The resultant optoelectronic device has a footprint that is more than two orders of magnitude smaller than today's typical DQPSK receivers, claims the company.
On the emitter side, Alcatel-Lucent's researchers from Alcatel-Thales III-V lab in France have demonstrated what they claim is the first integrated version of a laser and an electro-absorption modulator (EML) with a record bandwidth of 60 GHz. The company believes this result is a major step toward the next-generation 100-Gbit/sec source for Very Short Reach (VSR) transmission. In addition, this is also a potential low cost approach since researchers have also demonstrated its high operating temperature capability (43 Gbits/sec up to 70 ° C, IPRM'07)
Finally, Alcatel-Lucent's researchers from Alcatel-Thales III-V lab say they have realized a 42-GHz mode-locked laser source with a record wavelength tunability of 16 nm, keeping constant both the output power and the narrow pulse width of 2 picoseconds. These performances have been reached thanks to a new active layer made of Quantum Dots. In addition, the optical pulses are Fourier-transform limited, which is quite suitable for propagation in the fiber, note Alcatel-Lucent representatives. These features make such a laser very attractive for very high bit rate tunable optical transmission.
100 Gigabit Ethernet
In a related announcement, Alcatel-Lucent researchers also delivered three post-deadline papers that they claim successfully demonstrate new advances in optical transmission, paving the way for the future introduction of 100-Gigabit Ethernet optical networks.
According to the company, the major breakthroughs include the transmission of 12.8 Tbits/sec of data through a single optical fiber over a record distance of 2,550 km, a precursor for long-haul transmission at 100 Gbits/sec per wavelength; a pioneering 8-Tbit/sec data transmission using a simple and cost-effective 100-Gbit/sec channel modulation; and the first hybrid DWDM transmission of 100-Gbit/sec and 40-Gbit/sec channels in the same system, demonstrating the migration and coexistence capabilities of both.
"Positive results in these advanced tests further demonstrates our commitment to design the most efficient, highest bandwidth systems possible for the benefit of our customers," contends Romano Valussi, president of Alcatel-Lucent's optics activities. "The 100-Gbit/sec achievement further confirms our technology leadership in optical networking as a critical enabler of the IP network transformation."
The first experiment was achieved by Alcatel-Lucent's researchers in Villarceaux, France. They demonstrated a 12.8-Tbit/sec transmission on a single optical fiber, over the record distance of 2,550 km. As no previously reported experiment that had achieved more than 10 Tbits/sec were beyond 300 km, these results represent an improvement by a factor of more than eight, says the company. In this experiment, 160 WDM channels were modulated at 80 Gbits/sec each. Researchers note that the system involved several innovations, namely polarization division multiplexing, multi-level optical modulation, coherent detection, and powerful electrical signal processing.
The second result was achieved by Alcatel-Lucent's researchers from Stuttgart and Villarceaux. They realized an 8-Tbit/sec WDM transmission with 80Â channels, each modulated at 100 Gbits/sec, transmitted over 520 km. Such a density represents a breakthrough, claims the company, as the channels were very densely packed, separated by no more than 100 GHz from each other. This modulation is a simple, robust, and cost-effective way to generate and transmit a 100 Gbits/sec bandwidth by channel, says Alcatel-Lucent.
In the third experiment, Bell Labs researchers in New Jersey demonstrated what they claim is the first hybrid DWDM transmission of 100-Gbit/sec and 40-Gbit/sec channels in the same system, achieving a record overall spectral efficiency of 1.4 bits/s/Hz. This experiment is significant in that it demonstrates a feasible upgrade path for DWDM transport equipment to support 100-GbE channels using existing 50-GHz channel plans, says the company. These results are an extension of Alcatel-Lucent's recent demonstration of a similar capacity upgrade--where researchers replaced 10-Gbit/sec OOK channels with 40-Gbit/sec DQPSK channels, co-existing with 40-Gbit/sec DBPSK channels, in the same system (post-deadline paper at OFC/NFOEC 2007).