The Key Technology in Optical OFDM-PON

In this paper, a novel optical access network based on orthogonal frequency division multiplexing （OFDM） is proposed. An OFDMbased passive optical network （PON） uses multicarriers to carry different information that is transmitted to different optical network units （ONUs）. In this paper, system performance is analyzed for OFDMPON with different linewidths of the lightwave source, different optical signaltonoise ratio （OSNR）, different access distances, and different modulated formats. Colorlessness in the OFDMPON is also analyzed. Finally, a 40 Gb/s baseband OFDM-PON with two carriers and achieve errorfree performance over 25 km fiber transmission is proposed.

Bidirectional intensity modulated/direct detection optical OFDM WDM-PON system

In this paper, we have evaluated a bidirectional wavelength division multiplexing passive optical network(WDM-PON) employing intensity modulated/direct detection optical orthogonal frequency division multiplexing(IM/DD-OFDM). The proposed system employs 100 Gbit/s 16 quadrature amplitude modulation(16-QAM) downstream and 5 Gbit/s on-off keying(OOK) upstream wavelengths, respectively. The proposed system is considered low-cost as non-coherent IM/DD OFDM technology and a simple reflective semiconductor optical amplifier(RSOA) colorless transmitter are employed and no dispersion compensating fiber(DCF) is needed. Based on the bit error rate(BER) results of WDM signals, the proposed WDM-PON system can achieve up to 1.6 Tbit/s(100 Gbit/s/λ × 16 wavelengths) downstream transmission over a 30 km single mode fiber(SMF).

Field Transmission of 100G and Beyond:Multiple Baud Rates and Mixed Line Rates Using Nyquist-WDM Technology

In this paper, we describe successful joint experiments with Deutsche Telecom on long-haul transmission of 100G and beyond over standard single mode fiber （SSMF） and with in-line EDFA-only amplification. The transmission link consists of 8 nodes and 950 km installed SSMF in DT＇ s optical infrastructure. Laboratory SSMF was added for extended optical reach. The first field experiment involved transmission of 8 x 216.8 Gbit/s Nyquist-WDM signals over 1750 km with 21.6 dB average loss per span. Each channel, modulated by a 54.2 Gbaud PDM-CSRZ-QPSK signal, is on a 50 GHz grid, which produces a net spectral efficiency （SE） of 4 bit/s/Hz. We also describe mixed-data-rate transmission coexisting with 1T, 400G, and 100G channels. The 400G channel uses four independent subcarriers modulated by 28 Gbaud PDM-QPSK signals. This yields a net SE of 4 bit/s/Hz, and 13 optically generated subcarriers from a single optical source are used in the 1T channel with 25 Gbaud PDM-QPSK modulation. The 100G signal uses real-time coherent PDM-QPSK transponder with 15% overhead of soft-decision forward-error correction （SD-FEC）. The digital post filter and 1 -bit maximum-likelihood sequence estimation （MLSE） are introduced at the receiver DSP to suppress noise, linear crosstalk, and filtering effects. Our results show that future 400G and 1T channels that use Nyquist WDM can transmit over long-haul distances with higher SE and using the same QPSK format.

Terabit Superchannel Transmission: A Nyquist-WDM Approach

In this work, we focus on enhancing the network reach in terabit superchannel transmission by using a noise-suppressed Nyquist wavelength division multiplexing （NS-N-WDM） technique for polarization multiplexing quadrature phase-shift keying （PM-QPSK） subchannels at different symbol-rate-to-subchannel-spacing ratios up to 1.28. For the first time, we experimentally compare the transmission reach of this emerging technique with that of no-guard-interval coherent optical orthogonal frequency-division multiplexing （NGI-CO-OFDM） on the same testbed. At BER of 2 x 10 3 and 100 Gbit/s per channel, an NGI-CO-OFDM terabit superchannel can transmit over a maximum of 3200 km SMF-28 with EDFA-only amplification, and an NS-N-WDM terabit superchannel can transmit over a maximum of 2800 km SMF-28 with EDFA-only amplification. Assuming different coding gain, 11 x 112 Gbit/s per channel with hard-decision （HD） forward-error correction （FEC） and 11 × 128 Gbit/s per channel NS-N-WDM transmission with soft-decision （SD） FEC can be achieved over a maximum of 2100 km and 2170 km, respectively. These are almost equal and were achieved using digital noise filtering and one-bit maximum likelihood sequence estimation （MLSE） at the receiver DSP. Characteristics including the back-to-back （BTB） curves, the ADC bandwidth requirement, and the tolerance to unequal subchannel power of an NS-N-WDM superchannel were also evaluated.