Time And Wavelength Division Multiplexed Passive Optical Network Research Articles

115 Gbit/s downstream and 10 Gbit/s upstream TWDM-PON together with 11.25 Gbit/s wireless signal utilizing OFDM-QAM modulation

In this work, we propose and investigate a 115Gbit/s (4×28.75Gbit/s) downstream and 10 Gbit/s upstream time- and wavelength-division-multiplexing passive optical network (TWDM-PON) together with 11.25Gbit/s wireless broadcasting signal using multi-band orthogonal-frequency-division-multiplexing (OFDM) modulation within 10GHz bandwidth. Here, to compensate the power fading and chromatic dispersion in the higher frequency, we utilize a −0.7 chirp parameter Mach–Zehnder modulator (MZM) for the OFDM signal. Hence, negative power penalties of −0.3 and −0.4dB in the downstream and broadcasting wireless signals; and power penalty of 0.3dB in the upstream signal are measured at the bit error rate (BER) of 3.8×10−3 after 20km standard single mode fiber transmission without dispersion compensation.

ONU migration in dynamic Time and Wavelength Division Multiplexed Passive Optical Network (TWDM-PON)

We propose a novel Optical Network Units (ONU) migration mechanism within the Time and Wavelength Division Multiplexed PON (TWDM-PON) framework by rearranging the working ONUs to a minimum number of wavelengths and turning off the rest to save power. We show through simulation that the number of working wavelengths can be minimized up to a theoretical lower bound, e.g. 23%, under the typical ONU online profiles. We further investigate how the migration interval and delay influence the user Service Level Agreement (SLA). We find that under the example ONU online profiles, 99.99% ONU SLA can be realized with the migration delay of 1000 milli-seconds. However to realize 99.999% ONU SLA, the migration delay must be 100 milli-seconds or lower.

Characterization of energy-efficient and colorless ONUs for future TWDM-PONs

The Full Services Access Network group has recently selected the time and wavelength division multiplexed passive optical network (TWDM-PON) as the base technology solution for next-generation PON stage-2 (NG-PON2). Meeting the core requirements of NG-PON2 necessitates the following additional features in the transceivers of the optical network unit (ONU) that is located at subscriber premises: (a) legacy system compliant; (b) wavelength tunable; (c) cost-efficient; and (d) energy-efficient. To address these features, we investigate the properties of short-cavity vertical-cavity surface-emitting lasers (SC-VCSELs) for implementation as colorless ONU transmitters in future TWDM-PONs. Specifically, we investigate the tunability and transmission performance of the SC-VCSEL across the C-minus wavelength band for legacy system compliance. We report on error-free transmission across a 800 GHz tuning range with a potential aggregate upstream capacity of 80 Gbps over a system reach of 40 km and with a split ratio of 1:128 per wavelength channel. Results were achieved without dispersion compensation and electronic equalization. We also evaluate the energy efficiency of the SC-VCSEL in active, doze, and sleep mode. When in active mode, the SC-VCSEL transmitter block consumes 91.7% less power than a distributed feedback (DFB) laser transmitter block. When transitioning between doze and active modes, the transmitter block has a short settling time of only 205 ns, thus increasing the power-saving duration and consequently reducing the overall power consumption of the ONU. Through numerical analysis, evaluation of the energy-savings of the SC-VCSEL ONU over the DFB ONU under various modes of operation, demonstrates up to 84% of energy-savings. The capacity, tuning range, split ratio, system reach, and energy-savings arising from SC-VCSEL ONU implementation as reported in this work, exceed the minimum requirements of NG-PON2 for future TWDM-PON deployments.

Simultaneous DPSK demodulation and chirp management using delay interferometer in symmetric 40-Gb/s capability TWDM-PON system

We propose a symmetric 40-Gb/s aggregate rate time and wavelength division multiplexed passive optical network (TWDM-PON) system with the capability of simultaneous downstream differential phase shift keying (DPSK) signal demodulation and upstream signal chirp management based on delay interferometer (DI). With the bi-pass characteristic of DI, we experimentally demonstrate the bidirectional transmission of signals at 10-Gb/s per wavelength, and achieve negligible power penalties after 50-km single mode fiber (SMF). For the uplink transmission with DI, a ~11-dB optical power budget improvement at a bit error ratio of 1e-3 is obtained and the extinction ratio (ER) of signal is also improved from 3.4 dB to 13.75 dB. Owing to this high ER, the upstream burst-mode transmitting is successfully presented in term of time-division multiplexing. Moreover, in our experiment, a ~38-dB power budget is obtained to support 256 users with 50-km SMF transmission.

Symmetric 40-Gb/s TWDM-PON With 39-dB Power Budget

Time- and wavelength-division multiplexed passive optical network (TWDM-PON) has been selected by full service access networks as a primary solution for next generation PON stage 2 in April 2012. In this letter, we propose and demonstrate a symmetric 40-Gb/s TWDM-PON with 39-dB power budget. A reflective semiconductor optical amplifier is used in optical network unit as a pre-amplifier to enhance the sensitivity of downstream signals. For the upstream direction, a thermally-tuned directly modulated laser with 10-Gb/s modulation rate is used as upstream colorless source, and a chirp management filter is employed in optical line terminal to mitigate chromatic dispersion therefore enabling fiber transmission. Symmetric 40-Gb/s TWDM-PON is experimentally demonstrated with a power budget of 39 dB, which could support 25-km fiber transmission and 1:1000 splitting ratio.

Time- and Wavelength-Division Multiplexed Passive Optical Network (TWDM-PON) for Next-Generation PON Stage 2 (NG-PON2)

The next-generation passive optical network stage 2 (NG-PON2) effort was initiated by the full service access network (FSAN) in 2011 to investigate on upcoming technologies enabling a bandwidth increase beyond 10 Gb/s in the optical access network. The FSAN meeting in April 2012 selected the time- and wavelength-division multiplexed passive optical network (TWDM-PON) as a primary solution to NG-PON2. In this paper, we summarize the TWDM-PON research in FSAN by reviewing the basics of TWDM-PON and presenting the world's first full-system 40 Gb/s TWDM-PON prototype. After introducing the TWDM-PON architecture, we explore TWDM-PON wavelength plan options to meet the NG-PON2 requirements. TWDM-PON key technologies and their respective level of development are further discussed to investigate its feasibility and availability. The first full-system 40 Gb/s TWDM-PON prototype is demonstrated to provide 40 Gb/s downstream and 10 Gb/s upstream bandwidth. This full prototype system offers 38 dB power budget and supports 20 km distance with a 1:512 split ratio. It coexists with commercially deployed Gigabit PON (G-PON) and 10 Gigabit PON (XG-PON) systems. The operator-vendor joint test results testify that TWDM-PON is achievable by the reuse and integration of commercial devices and components.

A special issue on High-Speed Optical Transmission and Processing

The rapid growth in network capacity and traffic rates raises the significance of high-speed optical transmission and processing. Recent progress in optical communication systems in relation to multiplexing technologies in different degrees of freedom, advanced multi-level modulation formats, coherent detection and digital signal processing has facilitated dramatic increases in transmission capacity. To be compatible with high-speed optical transmission, highspeed optical processing has gained increased interest to enable fast data manipulation in the optical domain and avoid cumbersome optical-electrical-optical conversions at network nodes. Recent progress in nonlinear-optical devices has led to enhanced efficiency, flexibility and functionality of ultrafast nonlinear-optical signal processing. It is expected that these advances in high-speed optical transmission and processing will pave the way to achieve superior performance of high-speed optical networks. It is our intention to bring the research community’s attention to these hot topics in optical communication systems and networks. In this “Special Issue on High-Speed Optical Transmission and Processing”, 8 review articles and 2 research articles focusing on relevant subjects by internationally active groups in the field are specially presented. In the review articles, Dr. Xiang Zhou at AT&T Labs—Research in USA reviewed the recent progress in transmission of 400 Gb/s wavelength-division multiplexing (WDM) channels for optical networks with standard 50 GHz grid. The enabling modulation, coding, line system technologies, and the existing challenges were discussed. Dr. Zhengxuan Li at Shanghai Jiao Tong University talked about the key technologies and system proposals of time and wavelength-division multiplexing passive optical networks (TWDM-PON). Dr. Thomas G. Brown at University of Rochester in USA presented light field manipulation in the spatial degree of freedom, showing fascinating effects in focusing, propagation, illumination, and imaging. Dr. Chaotan Sima at University of Southampton in UK summarized progress and recent developments of photonic Hilbert transforms. Dr. Claudio Porzi at the TeCIP Institute of Scuola Superiore Sant’Anna di Pisa in Italy reviewed on the use of semiconductor optical amplifier-Mach-Zehnder interferometer (SOA-MZI) for photonic add/drop and switching operations. Dr. Li Huo at Tsinghua University reported recent works in 100 Gb/s signal regeneration and processing. Dr. Wei Jin at the Hong Kong Polytechnic University discussed different types of air-silica photonic crystal fibers (PCFs) and their wide applications. Dr. Sigang Yang showed recent development of fiber optical parametric oscillators (FOPO) based on highly nonlinear dispersion-shifted fiber. In the research articles, Dr. Xia Guo at Beijing University of Technology targeted scalable light-emitting diodes (LEDs) and vertical-cavity surface-emitting lasers (VCSELs) with tunnel-regenerated multi-active-region (TRMAR) structure. Dr. Muhammad Idrees Afridi at Beijing University of Posts and Telecommunications analyzed the impact of Rayleigh backscattering on single/dual feeder fiber wavelength-division multiplexing passive optical network (WDMPON) architectures. Overall, articles in this special issue cover the recent achievements of high-speed optical transmission and processing, particularly the latest emerging technologies and wide applications. We hope the readers will find them interesting and inspiring.

The Available Options for Wavelength Group Selection and Transceiver Design for Next Generation PON Stage 2 (NG-PON2)

The full service access network (FSAN) task group meeting was held in April 2012, where they agreed to adopt time and wavelength division multiplexed passive optical network (TWDM-PON) as a primary solution to NG-PON2. Major requirements includes at least 40 Gbit/s aggregate rate in downstream, 1:64 split ratio, 40 km differential reach, and at least 1 Gb/s access rate per optical network unit (ONU). In this paper, a performance analysis will be carried out for downstream 4-wavelengths group selection from S-band, L-band, and C-band. A comparison for optimal transmitter design is also investigated among probable options of chirp managed laser diode, Lithium Niobate (LiNbo3) Mach Zehnder modulator, besides examining tunable transceivers in contrary to remotely fed colorless ONUs.