A breakthrough paper on the fundamental capacity limits of the optical fiber taking non-linear propagation effects into account has been published by the OptCom Group. This comprehensive paper contains closed-form formulas addressing the so-called fiber non-linear Shannon limit for all coherent modulation formats, when using uncompensated transmission. The results address both lumped (EDFA) and ideal distributed amplification.

These formulas are likely to have a substantial impact on the strategic planning, research and eventually design of future complex coherent long-haul systems. Here below, one of the most significant results in the paper.

The paper can be downloaded from here.

Record PM-16QAM Nyquist-WDM Experiment:

Transmission of (16 x 112 Gb/s) PM-16QAM at 1.05 x (Symbol-Rate) Channel Spacing to 3,700 km

A breakthrough experiment has been carried out at the PhotonLab premises in Torino by the OptCom Group in collaboration with the Mario Boella Institute, CISCO Photonics and Sumitomo Electrics Corporation (SEC). 16 channels carrying 112 Gb/s PM-16QAM were transmitted to 3,700 km. Thanks to DAC-enabled spectral engineering, the transmitted channels were nearly perfectly rectangular and the channel spacing was only 5% away from the fundamental Nyquist limit. An ultra-low loss PSCF fiber fabricated by SEC was used. This experiment sets, for PM-16QAM, the current world record of spectral efficiency  and of spectral efficiency times distance.

The OptCom Group Coordinator, Prof. Pierluigi Poggiolini, remarked: "This is a landmark experiment, which proves that Nyquist-WDM, a technique proposed and pioneered by the OptCom Group and CISCO Photonics, is extremely effective, even with complex constellations like PM-16QAM, and will be the technology of choice for the next generation of ultra-long haul ultra-high capacity transmission systems".

In figure, the 16QAM constellations over the x and y  polarizations, after 2000 km. The experiment will be presented at OFC 2012:

Paper OTh3A.3. "Ultra-Long-Haul Transmission of 16x112 Gb/s Spectrally-Engineered DAC-Generated Nyquist-WDM PM-16QAM Channels with 1.05x(Symbol-Rate) Frequency Spacing"
Roberto Cigliutti; Antonello Nespola; Dario Zeolla; Gabriella Bosco; Andrea Carena; Vittorio Curri; Fabrizio Forghieri; Yoshinori Yamamoto; Takashi Sasaki; Pierluigi Poggiolini
 

You can download here the presentation for the ECOC 2011 Sunday Workshop "Link Design: a Forgotten Art", by Pierluigi Poggiolini, on "Analytical Modeling of the impact of non-linear effects on DWDM coherent Systems"

OptCom has published an IEEE Photonics Technology Letters paper reporting on a breakthrough non-linear fiber propagation model. Thanks to the model, coherent systems using uncompensated transmission can be analyzed and their performance easily and reliably predicted.

The paper is now available on the IEEE Xplore website: CLICK HERE

OptCom has performed a Terabit Superchannel experiment based on polarization-multiplexed 8QAM transmission (PM-8QAM).  The system consisted of 9 subcarriers transmitting at 138 Gb/s each with PM-8QAM. The launched Terabit Superchannel spectrum is shown in figure. The spacing was 28 GHz, 1.22 times the baud rate.

The experiment used 100 km spans of experimental SUMITOMO Electrics PSCF fiber, and Raman amplification. A transmission reach o 4070 km was achieved, at a BER better than 10^-2 on all subcarriers. This BER is compatible with last generation FECs. The net spectral efficiency, taking into account a 20% FEC overhead and 4% Ethernet protocol overhead, was 4.1 bit/s/Hz. The distance-times-spectral-efficiency product was a world record for PM-8QAM WDM systems, at the time of the posting (16700 b/s/Hz km).

A new ultra-long-haul Terabit Superchannel experiment has been performed at PhotonLab, achieving a frequency spacing equal to the Baud rate, record for conventional UDWDM systems employing neither Co-OFDM nor MAP/MLSE receivers.

Operating at 30 GBaud per subcarrier, 10 PM-QPSK subcarriers were sent to 9,000 km with a subcarrier spacing of just 30 GHz. Each subcarrier transmitted 120 Gb/s (100 Gb/s net data rate+20% overhead), for total of 1 Tb/s net data rate.

Z-PLUS(TM) pure-silica core fiber, provided by Sumitomo Electric Industries, was used, with mixed EDFA-Raman amplification. No optical dispersion compensation was performed. The span length was 100km.

In figure, see the reach vs. transmitted power of the Tb/s superchannel.

For partners and sponsors, please see the previous news report.

A record transmission experiment was performed at PhotonLab by the OptCom group, in cooperation with CISCO Photonics Monza, Oclaro Corporation and Linkra-Teleoptix. The experiment was also partially sponsored by the FP7 European Networks of Excellence EUROFOS and BONE, and by the Istituto Superiore Mario Boella in Turin.

A 1.2 Tbit/s superchannel consisting of ten subcarriers, each carrying 120 Gbit/s, was transmitted to 10,000 km. The transmission format was PM-QPSK at 30 GBaud. The subcarrier spacing was 33 GHz, i.e., 1.1 times the Baud rate. This experiment sets a new record for the parameter (spectral efficiency) x (distance). The previous record was 27000 while this experiment reaches 30000. Z-PLUS^(TM) pure-silica core fiber, provided by Sumitomo Electric Industries, and mixed EDFA-Raman amplification were used.

In a second experiment, 3 Terabit superchannels (30 subcarriers) were sent to 8,000 km (see launched signal power spectrum in figure).

The first Italian and possibly European 1 Tb/s per SuperChannel long-haul experiment was performed at PhotonLab by the OptCom Group, over 2600km.

A  1Tbit/s (1000 Gbit/s) superchannel was successfully transmitted over 2,600 km of installed fiber (a total of 41 spans), with a spectral efficiency of 3.3 b/s/Hz, using 10 PM-QPSK subcarriers spaced at 1.2 times the Baud rate. This results hints at the possibility of transmitting per-fiber capacity on the order 12-15 Tb/s (12000 Gb/s) over the C band and up to 30-40 Tb/s over the C+L bands.

To the left the power spectrum of the superchannel, where the 10 subcarriers are clearly visible. Each subcarrier transmits 100 Gbit/s.

This project is sponsored by the FP7 European Networks of

Excellence and , by FastWeb s.p.a. and by CISCO Photonics. It is also sponsored by

The first Italian implementation of a PDM-8QAM coherent optical transmission systems has been obtained by the OptCom Group at PhotonLab.

Below, the scattering diagrams for the x and y polarizations after DSP at 12.5 Gbaud (75 Gbit/s). The corresponding  OSNR is equal to 18 dB over 0.1 nm.  The plot is at the FEC threshold bit error rate of 1.5e-3.

The transmitter was obtained by a collaboration between our group and the Fraunhofer institute

inside the framework of the project POF-PLUS

The first italian WDM experiment of coherent transmission at 100 Gb/s per channel was performed by OptCom at PhotonLab. A total of 16 channels of 100 Gb/s PM-QPSK (1.6 Tb/s) were transmitted over installed dark fiber over 16 spans, for a total length of more than 1,000 km. Different dispersion maps were tested. Very good performance was obtained, thanks to high-performance modulators and balanced photodetectors.

To the left, the scattering diagram at 1,000 km of the center channel at a launched power of 0 dBm per channel and without any optical dispersion compensation. PM-QPSK confirmed its robustness. to both linear and non-linear impairments.

The experiment was supported by the project

A. Carena, V. Curri, P. Poggiolini, F Forghieri, "Guard-Band for 111 Gbit/s coherent PM-QPSK channels on legacy fiber links carrying 10 Gbit/s IMDD channels", OFC 2009, San Diego (CA), paper OThR7.

Click here to download the Power Point presentation.
 

Transmission of 100 Gb/s PDM-QPSK was achieved by the OptCom Group over installed fiber belonging to the Torino Metro Network of the operator Fastweb, up to 2000 km, using a recirculating loop scheme. 32 recirculations of 63 km each were used. The experiment was carried out in cooperation with the Heinrich-Hertz Istitute (HHI) of Berlin.

This is possibly the first long-haul coherent experiment at 100 Gb/s carried out in Italy. It was sponsored by the EUROFOS project.

The OptCom Group participated in the EUROFOS project plenary meeting that took place in Paris, on Jan 22nd and 23rd. Substantial joint experimental activity on 100Gb/s coherent transmission was agreed upon with major international partners of the EURO-FOS Consortium, to be carried out at PhotonLab. The first results will be available by March 2009. Click on the logo to learn more about EUROFOS.

A prototype of a 100 Gb/s PDM-QPSK coherent optical transmission systems has been built by the OptCom Group at PhotonLab, possibly the first such system implemented in Italy.

Below, the scattering diagrams for the x and y polarizations after DSP. The plot is at the FEC threshold bit error rate of 2e-3. The corresponding ONSR is 15 dB over 0.1 nm.

SEMINAR ON:

Kaleidon, the new Telecom Italia Photonic Backbone

Politecnico di Torino

Wednesday,
February 15th 2012,

LINGOTTO Premises, ROOM 402, 14:00-17:00

Dr. Marco Schiano, from Telecom Italia, will deliver a seminar (in English) on the evolution of the backbone networks implemented by Telecom Italia over the last 15 years and an overview of its new flexible photonic backbone, incorporating such new technologies as optical routing and coherent transmission, which is currently being deployed.

The seminar is open to all attendees. No reservation nor confirmation is required.

Politecnico di Torino

Thursday, January 26th 2012, ROOM 10D, 9:30-11:30

Roberto Cigliutti, formerly with Pirelli Submarine Systems, will deliver a seminar (in English) on long-haul submarine systems. The specific features of the design, fabrication, deployment and maintenance of submarine systems will be discussed. Actual parts of a submarine repeater will also be shown, as well as samples of submarine cables.

The seminar is open to all attendees. No reservation required.