Showing papers on "Wavelength-division multiplexing published in 2012"

Mode-Division Multiplexing Over 96 km of Few-Mode Fiber Using Coherent 6 $\,\times\,$ 6 MIMO Processing

Abstract: We report simultaneous transmission of six spatial and polarization modes, each carrying 40 Gb/s quadrature-phase-shift-keyed channels over 96 km of a low-differential group delay few-mode fiber. The channels are successfully recovered by offline DSP based on coherent detection and multiple-input multiple-output processing. A penalty of ;28 dB.

1.01-Pb/s (12 SDM/222 WDM/456 Gb/s) Crosstalk-managed Transmission with 91.4-b/s/Hz Aggregate Spectral Efficiency

Abstract: (40-Word Limit): We demonstrate 1.01-Pb/s transmission over 52 km with the highest aggregate spectral efficiency of 91.4 b/s/Hz by using low-crosstalk one-ring-structured 12-core fiber. Our multi-core fiber and compact fan-in/fan-out devices are designed to support high-order modulation formats up to 32-QAM in SDM transmission.

Mode-division multiplexed transmission with inline few-mode fiber amplifier.

Abstract: We demonstrate mode-division multiplexed WDM transmission over 50-km of few-mode fiber using the fiber’s LP01 and two degenerate LP11 modes. A few-mode EDFA is used to boost the power of the output signal before a few-mode coherent receiver. A 6×6 time-domain MIMO equalizer is used to recover the transmitted data. We also experimentally characterize the 50-km few-mode fiber and the few-mode EDFA.

Power consumption modeling in optical multilayer networks

Abstract: The evaluation of and reduction in energy consumption of backbone telecommunication networks has been a popular subject of academic research for the last decade. A critical parameter in these studies is the power consumption of the individual network devices. It appears that across different studies, a wide range of power values for similar equipment is used. This is a result of the scattered and limited availability of power values for optical multilayer network equipment. We propose reference power consumption values for Internet protocol/multiprotocol label switching, Ethernet, optical transport networking and wavelength division multiplexing equipment. In addition we present a simplified analytical power consumption model that can be used for large networks where simulation is computationally expensive or unfeasible. For illustration and evaluation purpose, we apply both calculation approaches to a case study, which includes an optical bypass scenario. Our results show that the analytical model approximates the simulation result to over 90% or higher and that optical bypass potentially can save up to 50% of power over a non-bypass scenario.

19-core fiber transmission of 19×100×172-Gb/s SDM-WDM-PDM-QPSK signals at 305Tb/s

Abstract: A novel free-space coupling system combined with a multi-core fiber enables up-scaling to a record space-division-multiplexed (SDM) channel number of 19. We achieve 305-Tb/s transmission over 10.1 km using 19-SDM, 100-WDM PDM-QPSK signals.

A 90nm CMOS integrated Nano-Photonics technology for 25Gbps WDM optical communications applications

Abstract: The first sub-100nm technology that allows the monolithic integration of optical modulators and germanium photodetectors as features into a current 90nm base highperformance logic technology node is demonstrated. The resulting 90nm CMOS-integrated Nano-Photonics technology node is optimized for analog functionality to yield power-efficient single-die multichannel wavelength-mulitplexed 25Gbps transceivers.

Mode-Division Multiplexing of 2 $\,\times\,$ 100 Gb/s Channels Using an LCOS-Based Spatial Modulator

Abstract: We demonstrate one of the first experiments of optical transmission based on mode-division multiplexing over a few-mode optical fiber. The mode multiplexer and demultiplexer are based on a programmable liquid crystal on silicon panel. Using this system, we transmit two 100 Gb/s polarization division multiplexed quaternary phase-shift keying data streams modulated on two different modes of the prototype few-mode fiber. At the receiver, a set of optical coherent detectors with DSP including multiple-input multiple-output algorithms recover the signal and permit to mitigate the crosstalk stemming from imperfect mode conversion.

Space-division multiplexed transmission over 4200-km 3-core microstructured fiber

Abstract: We experimentally demonstrate multiple-input-multiple-output transmission of a combined 3-space-, and 2-polarization-, and 5-wavelength-division multiplex in a 3-core microstructured fiber over 4200 km. This is the record transmission distance for spatial-division multiplexing in a fiber.

Optical Networking Beyond WDM

Abstract: Wavelength-division multiplexing (WDM) has been the workhorse of data networks, accommodating exponential traffic growth for two decades. Recently, however, progress in WDM capacity research has markedly slowed down as experiments are closely approaching fundamental Shannon limits of nonlinear fiber transmission. Space-division multiplexing (SDM) is expected to further scale network capacities, using parallel strands of single-mode fiber, uncoupled or coupled cores of multicore fiber, or even individual modes of few-mode fiber in combination with multiple-input-multiple-output (MIMO) digital signal processing. At the beginning of a new era in optical communications, we review initial research in SDM technologies and address some of the key challenges ahead.

Terabit Optical Access Networks Based on WDM-OFDMA-PON

Abstract: Next-generation optical access networks are envisioned to evolve into a converged, high-speed, multiservice platform supporting residential, business, mobile backhaul, and special purpose applications. Moreover, bandwidth demand projections suggest that terabit aggregate capacity may need to be reached in such next-generation passive optical networks (PON). To satisfy these requirements while leveraging the large investments made in existing fiber plants, a wavelength division multiplexed (WDM)-based long-reach PON architecture combined with a multiple access technology that features a passive last-mile split, large per-λ speeds, and statistical bandwidth multiplexing can be exploited. In this paper, the first terabit PON based on hybrid WDM orthogonal frequency division multiple access (OFDMA) technology is proposed and experimentally verified. To enable high-speed, long-reach transmission with simplified optical network unit (ONU)-side digital signal processing, multiband OFDMA with ONU-side sub-band selectivity is proposed. Design challenges and tradeoffs between analog and digital domain sub-band combining and selection are also discussed. Finally, the experimental setup and results of the first 1.2 Tb/s (1 Tb/s after overhead) symmetric WDM-OFDMA-PON over 90 km straight single-mode fiber and 1:32 passive split, featuring multiband OFDMA, digitally selective ONUs, and a coherent-receiver OLT are presented and analyzed. By supporting up to 800 ONUs with 1.25/10 Gb/s guaranteed/peak rates and exhibiting a record rate-distance product achieved in long-reach PON, the demonstrated architecture may be viewed as promising for future converged terabit optical metro/access.

A Large Serial Time-Division Multiplexed Fiber Bragg Grating Sensor Network

Abstract: We demonstrated a wavelength scanning time division multiplexing of 1000 ultra-weak fiber Bragg gratings (FBG) for distributed temperature sensing. The strong multiplexing capability and low crosstalk of the ultra-weak FBG sensors is investigated through both theoretical analysis and experiment. An automated FBG fabrication system was developed for fast 1000-FBG fabrication. The measurement accuracy of Bragg wavelengths for more than 80% FBGs is less than 20 pm, corresponding to 2 $^{\circ}$ C in temperature.

73.7 Tb/s (96X3x256-Gb/s) mode-division-multiplexed DP-16QAM transmission with inline MM-EDFA

Abstract: We show transmission of a 73.7 Tb/s (96×3×256-Gb/s) DP-16QAM mode-division-multiplexed signal over 119km of few-mode fiber with inline multi-mode EDFA, using 6x6 MIMO digital signal processing. The total demonstrated net capacity is 57.6 Tb/s (SE 12 bits/s/Hz).

Single-laser 32.5 Tbit/s Nyquist WDM transmission

Abstract: We demonstrate single-laser 32.5 Tbit/s 16QAM Nyquist wavelength division multiplexing transmission over a total length of 227 km of SMF-28 without optical dispersion compensation. A number of 325 optical carriers is derived from a single laser and encoded with dual-polarization 16QAM data using sinc-shaped Nyquist pulses. As we use no guard bands, the carriers have a spacing of 12.5 GHz equal to the symbol rate or Nyquist bandwidth of the data. We achieve a net spectral efficiency of 6.4 bit/s/Hz using a software-defined transmitter, which generates the electric drive signals for the electro-optic modulator in real time.

Joint Digital Signal Processing Receivers for Spatial Superchannels

Abstract: We discuss the advantages of spatial superchannels for future terabit networks based on space-division multiplexing (SDM), and demonstrate reception of spatial superchannels by a coherent receiver utilizing joint digital signal processing (DSP). In a spatial superchannel, the SDM modes at a given wavelength are routed together, allowing a simplified design of both transponders and optical routing equipment. For example, common-mode impairments can be exploited to streamline the receiver's DSP. Our laboratory measurements reveal that the phase fluctuations between the cores of a multicore fiber are strongly correlated, and therefore constitute such a common-mode impairment. We implement master-slave phase recovery of two simultaneous 112-Gbps subchannels in a seven-core fiber, demonstrating reduced processing complexity with no increase in the bit-error ratio. Furthermore, we investigate the feasibility of applying this technique to subchannels carried on separate single-mode fibers, a potential transition strategy to evolve today's fiber networks toward future networks using multicore fibers.

Tunable high-channel-count bandpass plasmonic filters based on an analogue of electromagnetically induced transparency

Abstract: We have proposed a novel type of bandpass plasmonic filter consisting of metal-insulator-metal bus waveguides coupled with a series of side-coupled cavities and stub waveguides. The theoretical modeling demonstrates that our waveguide-resonator system performs a plasmonic analogue of electromagnetically induced transparency (EIT) in atomic systems, as is confirmed by numerical experiments. The plasmonic EIT-like response enables the realization of nanoscale bandpass filters with multiple channels. Additionally, the operating wavelengths and bandwidths of our filters can be efficiently tuned by adjusting the geometric parameters such as the lengths of stub waveguides and the coupling distances between the cavities and stub waveguides. The ultracompact configurations contribute to the achievement of wavelength division multiplexing systems for optical computing and communications in highly integrated optical circuits.

A 2-D Discrete-Time Model of Physical Impairments in Wavelength-Division Multiplexing Systems

Abstract: Dense wavelength-division multiplexing (DWDM) is a promising approach to design ultrahigh-capacity fiber-optic communication systems ( >; nn50 Tb/s). However, DWDM gives rise to severe physical impairments that adversely affect system performance. To mitigate various physical impairments in DWDM systems and exploit their system capacity, there is a need to develop a 2-D (time and wavelength) discrete-time input-output model of physical impairments that can become the foundation of signal processing for optical communications. This paper develops such a model based on the Volterra series transfer function (VSTF) method. We overcome the well-known triple integral problem associated with the VSTF method and reduce it to a simple integral. This model takes into account multiple channel effects, fiber losses, frequency chirp, optical filtering, and photo detection, which are ignored in the current literature. The model is in excellent agreement with results obtained by split-step Fourier simulation. Furthermore, with this model, we define coefficients that capture intersymbol interference, interchannel interference, self-phase modulation, intrachannel cross-phase modulation (XPM), intrachannel four-wave mixing (FWM), XPM, and FWM to characterize the impact of these effects individually on the system performance. We also apply this model to analyze the effects of varying system parameters and pulse shapes on the individual physical impairments.

Mode-selective couplers for few-mode optical fiber networks

Abstract: The excitation and separation of individual modes in a few-mode optical fiber network can be realized using mode-selective couplers. For excitation at the beginning of the fiber, two-core mode-selective couplers can be used, while at the end of the fiber, either two- or three-core mode-selective couplers are required for demultiplexing of the field symmetric or field asymmetric modes, respectively. Both analytical and numerical solutions are presented to quantify the mode-selective functionality.

OFDM Based Superchannel Transmission Technology

Abstract: This paper reviews recent advances in the generation, detection and transmission of orthogonal-frequency-division-multiplexing (OFDM) based superchannels, enabled by efficient and powerful digital signal processors. The use of OFDM to form a superchannel can be (1) at the modulation stage by naturally realizing a square-like signal spectral shape to allow close packing of multiple modulated signals, and/or (2) at the optical multiplexing stage by seamlessly multiplexing these modulated signals. This paper reviews recent advances in this field. Several OFDM-based superchannel architectures are described and compared.

Space Division Multiplexed Transmission of 109-Tb/s Data Signals Using Homogeneous Seven-Core Fiber

Abstract: We achieved record 109-Tb/s transmission over 16.8 km, using space division multiplexing (SDM) together with conventional multiplexing technology. 7-core SDM, 97 WDM (100-GHz spacing), 2 × 86 Gb/s PDM-QPSK signals were used. The spectral efficiency was 11.2 b/s/Hz. SDM transmission was realized using a multi-core fiber with ultra-low-crosstalk (less than -90.0 dB/km at 1550 nm) and high performance SDM MUX/DEMUX. The overall SDM crosstalk of -53 dB caused almost no penalty for the PDM-QPSK transmission.

Optical traffic grooming in OFDM-based elastic optical networks [Invited]

Abstract: Orthogonal frequency-division multiplexing (OFDM) is a multi-carrier modulation technology that transmits a high-speed data stream using multiple spectrally overlapped lower-speed subcarriers. Optical OFDM (O-OFDM) technology is a promising candidate for future high-speed optical transmission. Based on O-OFDM, a novel elastic optical network architecture with immense flexibility and scalability in spectrum allocation and data rate accommodation can be built to support diverse services and the rapid growth of Internet traffic. This architecture can provide various services directly at the optical layer in a spectrum-efficient way through bandwidth-elastic optical paths. However, carrying various data rate services using a single type of bandwidth-variable transponder might not be cost-efficient. Electrical traffic grooming is a traditional approach for sub-wavelength service accommodation in wavelength division multiplexing networks. However, it places additional electrical switching and optical-electrical-optical conversion requirements on the network, which may lead to higher cost and energy consumption. In contrast, grooming traffic optically is an attractive option for elastic optical networks. In this paper, we propose a novel optical grooming approach to aggregate and distribute traffic directly at the optical layer in OFDM-based elastic optical networks. We study routing and spectrum allocation algorithms of optical grooming to show the benefits of this approach. Our results demonstrate that significant transmitter and spectrum savings can be achieved by the optical grooming versus the non-grooming scenario, and a trade-off between optimizing the number of transmitters and optimizing spectrum usage should be considered during network planning.

High Capacity/Spectral Efficiency 101.7-Tb/s WDM Transmission Using PDM-128QAM-OFDM Over 165-km SSMF Within C- and L-Bands

Abstract: We experimentally demonstrate 101.7-Tb/s transmission over 355 km spans of standard single-mode fiber (SSMF) at a net spectral efficiency of 11 b/s/Hz. A total of 370 dense wavelength-division multiplexed (DWDM) channels spanning the optical C- and L-bands spaced at 25 GHz were used. Each 25-GHz channel were subdivided into four subbands, with each subband carrying a 73.5-Gb/s orthogonal frequency-division multiplexed (OFDM) signal modulated with polarization-division-multiplexing (PDM) 128-ary quadrature amplitude modulation (QAM) at each modulated subcarrier. This experiment was enabled by digital signal processing (DSP) pre-equalization of transmitter impairments, all Raman amplification, heterodyne coherent detection, and DSP postequalization of the channel and receiver impairments, including pilot-based phase noise compensation.

Spectrum allocation policy modeling for elastic optical networks

Abstract: Today, optical transmission technologies are able to support 400Gbps over a single optical channel. However, this capacity cannot fit in the current fixed frequency grid optical spectrum. On the other hand, high rate optical channels have to co-exist with different ranges of line rates in order to serve heterogeneous bandwidth requests from variety of internet applications. Today's fixed rate and rigid frequency grid optical transmission systems cause over provisioning, where usually more spectral resources are provided than necessary.

WDM/SDM transmission of 10 x 128-Gb/s PDM-QPSK over 2688-km 7-core fiber with a per-fiber net aggregate spectral-efficiency distance product of 40,320 km⋅b/s/Hz

Abstract: We demonstrate 2688-km multi-span transmission using wavelength-division multiplexing (WDM) of ten 50-GHz spaced 128-Gb/s PDM-QPSK signals, space-division multiplexed (SDM) in a low-crosstalk 76.8-km seven-core fiber, achieving a record net aggregate per-fiber-spectral-efficiency-distance product of 40,320 km·b/s/Hz. The demonstration was enabled by a novel core-to-core signal rotation scheme implemented in a 7-fold, synchronized recirculating loop apparatus.

High-Speed Quantum Key Distribution System for 1-Mbps Real-Time Key Generation

Abstract: A high-speed quantum key distribution (QKD) system has been developed with the goal of a 1-Mbps final secure key generation rate under 10-dB transmission loss, which corresponds to 50 km of standard single mode fiber. For the purpose of speeding-up all processes in QKD sequence, we apply a wavelength-division-multiplexing (WDM) technique using the colorless interferometric technique and a key distillation hardware (HW) engine. We establish a novel WDM scheme, sharing interferometers and their temperature regulators over multiple channels, which enables us to increase the number of channels with a small impact on system cost and size. To generate a secure key while satisfying both high speed and high security, we develop a key distillation HW engine which enables us to execute key distillation with 1-Mbit code length in real time. We have experimentally evaluated the performance of the developed system through installed fiber. By operating three wavelength channels, a new, world leading key generation rate of greater than 200 kbps over a 14.5-dB transmission loss has been achieved.

Colorless coherent receiver using 3x3 coupler hybrids and single-ended detection

Abstract: We demonstrate a single-ended colorless coherent receiver using symmetric 3x3 couplers for optical hybrids. We show that the receiver can achieve colorless reception of fifty-five 112-Gb/s polarization-division-multiplexed quadrature-phase-shift-keyed (PDM-QPSK) channels with less than 1-dB penalty in the back-to-back operation. The receiver also works well in a long-haul wavelength-division-multiplexed (WDM) transmission system over 2560-km TrueWave® REACH fiber.

OSNR monitoring for QPSK and 16-QAM systems in presence of fiber nonlinearities for digital coherent receivers

Abstract: OSNR monitoring is indispensable for coherent systems to ensure robust, reliable network operation and potentially enable impairment-aware routing for future dynamic optical networks. In a long-haul transmission link with chromatic dispersion (CD) and fiber nonlinearity, it is difficult to distinguish between amplifier noise and fiber nonlinearity induced distortions from received signal distributions even after various transmission impairment compensation techniques, thus resulting in grossly inaccurate OSNR estimates. Based on the received signal distributions after carrier phase estimation (CPE), we propose to characterize the nonlinearity-induced amplitude noise correlation across neighboring symbols and incorporate such information into error vector magnitude (EVM) calculation to realize fiber nonlinearity-insensitive OSNR monitoring. For a transmission link up to 1600 km and signal launched power up to 2 dBm, experimental results for 112 Gb/s polarization-multiplexed quadrature phase-shift keying (PM-QPSK) demonstrate an OSNR monitoring range of 10-24 dB with a maximum estimation error below 1 dB. For 224 Gb/s PM-16-quadrature amplitude modulation (PM-16-QAM) systems, simulation results demonstrate an OSNR monitoring range of 18-28 dB with a maximum estimation error below 1 dB. Tolerance of the proposed OSNR monitoring technique to different pulse shapes, timing phase offsets, polarization dependent loss (PDL), polarization-mode dispersion (PMD) and WDM effects are also investigated through simulations.

High-speed wavelength-division multiplexing quantum key distribution system

Abstract: A high-speed quantum key distribution system was developed with the wavelength-division multiplexing (WDM) technique and dedicated key distillation hardware engines. Two interferometers for encoding and decoding are shared over eight wavelengths to reduce the system’s size, cost, and control complexity. The key distillation engines can process a huge amount of data from the WDM channels by using a 1 Mbit block in real time. We demonstrated a three-channel WDM system that simultaneously uses avalanche photodiodes and superconducting single-photon detectors. We achieved 12 h continuous key generation with a secure key rate of 208 kilobits per second through a 45 km field fiber with 14.5 dB loss.

Modeling and characterization of a few-mode EDFA supporting four mode groups for mode division multiplexing.

Abstract: Numerical and experimental study of a Few-Mode (FM) Erbium Doped Fiber Amplifier (EDFA) suitable for mode division multiplexing (MDM) is reported. Based on numerical simulations, a Few-Mode Erbium Doped Fiber (FM-EDF) has been designed to amplify four mode groups and to equally amplify LP11 and LP21 mode groups with gains greater than 20 dB and with a differential modal gain of less than 1 dB. Experimental results confirmed the simulations with a good concordance. This modal gain equalization is obtained by tailoring the erbium spatial distribution in the fiber core with a ring-shaped profile.