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Showing papers on "Wavelength-division multiplexing published in 2010"


Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate the first monolithically integrated CMOS-compatible source by creating an optical parametric oscillator formed by a silicon nitride ring resonator on silicon.
Abstract: Silicon photonics enables the fabrication of on-chip, ultrahigh-bandwidth optical networks that are critical for the future of microelectronics1,2,3 Several optical components necessary for implementing a wavelength division multiplexing network have been demonstrated in silicon However, a fully integrated multiple-wavelength source capable of driving such a network has not yet been realized Optical amplification, a necessary component for lasing, has been achieved on-chip through stimulated Raman scattering4,5, parametric mixing6 and by silicon nanocrystals7 or nanopatterned silicon8 Losses in most of these structures have prevented oscillation Raman oscillators have been demonstrated9,10,11, but with a narrow gain bandwidth that is insufficient for wavelength division multiplexing Here, we demonstrate the first monolithically integrated CMOS-compatible source by creating an optical parametric oscillator formed by a silicon nitride ring resonator on silicon The device can generate more than 100 new wavelengths with operating powers below 50 mW This source can form the backbone of a high-bandwidth optical network on a microelectronic chip A monolithically integrated CMOS-compatible source is demonstrated using an optical parametric oscillator based on a silicon nitride ring resonator on silicon Generating more than 100 wavelengths simultaneously and operating at powers below 50 mW, scientists say that it may form the basis of an on-chip high-bandwidth optical network

1,052 citations


Book ChapterDOI
25 Oct 2010
TL;DR: This work introduces the Routing, Modulation Level and Spectrum Allocation (RMLSA) problem, as opposed to the typical Routing and Wavelength Assignment (RWA) problem of traditional WDM networks, proves that it is also NP-complete and presents various algorithms to solve it.
Abstract: Orthogonal Frequency Division Multiplexing (OFDM) has recently been proposed as a modulation technique for optical networks, because of its good spectral efficiency, flexibility, and tolerance to impairments. We consider the planning problem of an OFDM optical network, where connections are provisioned for their requested rate by elastically allocating spectrum using a variable number of OFDM subcarriers and choosing an appropriate modulation level taking into account the transmission distance. Using algorithms developed in our previous works, we evaluate the spectrum utilization gains that can be obtained by utilizing the elastic bandwidth allocation of OFDM, when compared to a traditional WDM network.

537 citations


Journal ArticleDOI
TL;DR: An overview of different techniques to optically transport mm-wave wireless signals and to overcome impairments associated with the transport of the wireless signals is presented and the different designs of subsystems for integrating fiber-wireless technology onto existing optical infrastructure are reviewed.
Abstract: Hybrid fiber-wireless networks incorporating WDM technology for fixed wireless access operating in the sub-millimeter-wave and millimeter-wave (mm-wave) frequency regions are being actively pursued to provide untethered connectivity for ultrahigh bandwidth communications. The architecture of such radio networks requires a large number of antenna base-stations with high throughput to be deployed to maximize the geographical coverage with the main switching and routing functionalities located in a centralized location. The transportation of mm-wave wireless signals within the hybrid network is subject to several impairments including low opto-electronic conversion efficiency, fiber chromatic dispersion and also degradation due to nonlinearities along the link. One of the major technical challenges in implementing such networks lies in the mitigation of these various optical impairments that the wireless signals experience within the hybrid network. In this paper, we present an overview of different techniques to optically transport mm-wave wireless signals and to overcome impairments associated with the transport of the wireless signals. We also review the different designs of subsystems for integrating fiber-wireless technology onto existing optical infrastructure.

510 citations


Journal ArticleDOI
Steven Gringeri1, B. Basch1, Vishnu Shukla1, R. Egorov1, Tiejun J. Xia1 
TL;DR: The architectures and various ROADM implementations including colorless, directionless, and contentionless add/drop structures are presented and the effect of scaling bit rates beyond 100 Gb/s onROADM architectures is reviewed including providing variable channel bandwidth depending on bit rate.
Abstract: Flexibility to support mesh topologies, dynamic capacity allocation, and automated network control and light path setup are key elements in the design of next-generation optical transport networks. To realize these capabilities, reconfigurable optical add/drop multiplexers with dynamic add/drop structures, embedded control planes, and lightpath characterization are required. This article presents the architectures and various ROADM implementations including colorless, directionless, and contentionless add/drop structures. The effect of scaling bit rates beyond 100 Gb/s on ROADM architectures is reviewed including providing variable channel bandwidth depending on bit rate. Automated provisioning and restoration using the GMPLS control plane and optical measurement approaches for lightpaths are also discussed.

484 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of finite analog-to-digital converter resolution, laser frequency offset, laser phase noise, and narrowband optical filtering on the performance of PDPM 16-ary quadrature amplitude modulation (16-QAM) were investigated.
Abstract: We discuss the generation, wavelength-division-multiplexed (WDM) long-haul transmission, and coherent detection of 112-Gb/s polarization-division-multiplexed (PDM) 16-ary quadrature amplitude modulation (16-QAM) at a line rate of 14 Gbaud and spectral efficiencies beyond 4 b/s/Hz. We describe the (off-line) digital signal processing and blind filter adaptation algorithms used in our intradyne receiver and characterize its performance using both simulated and measured 16-QAM waveforms. We measure a required optical signal-to-noise ratio of 20.2 dB (0.1-nm reference bandwidth; 10-3 bit-error ratio), 3.2-dB off the theoretical limit. We study the effects of finite analog-to-digital converter resolution, laser frequency offset, laser phase noise, and narrowband optical filtering. Our experiments on a 25-GHz WDM grid (4.1-b/s/Hz spectral efficiency) reveal a 1-dB penalty after 7 passes though reconfigurable optical add/drop multiplexers (ROADMs) and an achievable transmission reach of 1022 km of uncompensated standard single-mode fiber. At a spectral efficiency of 6.2 b/s/Hz (16.67-GHz WDM channel spacing) a transmission reach of 630 km is attained.

381 citations


Journal ArticleDOI
TL;DR: The two techniques for generating polarization-multiplexed quadrature phase-shift keying with a high spectral efficiency have the same sensitivity and SE under idealized assumptions, but it is found that CO-OFDM requires a much larger receiver bandwidth and proportionally faster speed of the analog-to-digital converters.
Abstract: We compare by simulation the performance of two techniques for generating polarization-multiplexed quadrature phase-shift keying with a high spectral efficiency (SE). The first is based on coherent optical orthogonal frequency-division multiplexing (CO-OFDM). The second, which we call Nyquist wavelength-division multiplexing (N-WDM), is based on the use of optical pulses having an “almost” rectangular spectrum, with bandwidth ideally equal to the Baud-rate. We show that the two techniques have the same sensitivity and SE under idealized assumptions. However, we found that CO-OFDM requires a much larger receiver bandwidth and proportionally faster speed of the analog-to-digital converters. We also tested CO-OFDM and N-WDM over long-haul nonlinear links and found N-WDM to outperform CO-OFDM in this case, too.

328 citations


Journal ArticleDOI
Ezra Ip1
TL;DR: In this article, the authors compare single carrier (SC) versus orthogonal frequency-division multiplexing (OFDM) for polarization-multiplexed transmission and show that at realistic data rates and transmission distances, polarization mode dispersion does not significantly degrade the performance of digital backpropagation and can be mitigated by a post-BP linear equalizer.
Abstract: Digital backpropagation (BP) is a universal method for jointly compensating dispersion and nonlinear impairments in optical fiber and is applicable to signals of any modulation format. In this paper, we compare single carrier (SC) versus orthogonal frequency-division multiplexing (OFDM) for polarization-multiplexed transmission. We show that at realistic data rates and transmission distances, polarization mode dispersion does not significantly degrade the performance of BP and can be mitigated by a post-BP linear equalizer. Dispersion unmanaged transmission can significantly reduce nonlinearity, and in this transmission regime, SC and OFDM have similar nonlinear tolerance. Multichannel BP is effective at mitigating interchannel nonlinearity for point-to-point links.

267 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a design method for mixed line rate (MLR) optical networks with transceivers employing different modulation formats, and demonstrated the tradeoff between a transceiver's cost and its optical reach in overall network design.
Abstract: With the growth of traffic volume and the emergence of various new applications, future telecom networks are expected to be increasingly heterogeneous with respect to applications supported and underlying technologies employed. To address this heterogeneity, it may be most cost effective to set up different lightpaths at different bit rates in such a backbone telecom mesh network employing optical wavelength-division multiplexing. This approach can be cost effective because low-bit-rate services will need less grooming (i.e., less multiplexing with other low-bit-rate services onto high-capacity wavelengths), while a high-bit-rate service can be accommodated directly on a wavelength itself. Optical networks with mixed line rates (MLRs), e.g., 10/40/100 Gb/s over different wavelength channels, are a new networking paradigm. The unregenerated reach of a lightpath depends on its line rate. So, the assignment of a line rate to a lightpath is a tradeoff between its capacity and transparent reach. Thus, based on their signal-quality constraints (threshold bit error rate), intelligent assignment of line rates to lightpaths can minimize the need for signal regeneration. This constraint on the transparent reach based on threshold signal quality can be relaxed by employing more advanced modulation formats, but with more investment. We propose a design method for MLR optical networks with transceivers employing different modulation formats. Our results demonstrate the tradeoff between a transceiver's cost and its optical reach in overall network design.

235 citations


Journal ArticleDOI
TL;DR: Recent state-of-the-art research on the enabling technologies needed to realize future WDM-PON and WDM/TDM-Pon systems are reviewed, and future directions toward practical PON systems are discussed.
Abstract: Wavelength-division multiplexing (WDM) technologies are expected to play a key role in realizing the next generation scalable and flexible passive optical networks (PONs). One candidate is WDM-PON, in which each optical network unit (ONU) uses a different wavelength, i.e., a unique wavelength, in each direction to communicate with the optical line terminal. Another candidate is WDM/time-division multiplexing (TDM)-PON; it combines WDM with TDM technology. This paper reviews recent state-of-the-art research on the enabling technologies needed to realize future WDM-PON and WDM/TDM-PON systems, and discusses future directions toward practical PON systems.

171 citations


Book
04 Mar 2010
TL;DR: This unique book represents a coherent and comprehensive introduction to the fundamentals of optical communications, signal processing and coding for optical channels, and is the first to integrate the basics of coding theory with the fundamentalsof optical communication.
Abstract: In order to adapt to the ever-increasing demands of telecommunication needs, todays network operators are implementing 100 Gb/s per dense wavelength division multiplexing (DWDM) channel transmission At those data rates, the performance of fiberoptic communication systems is degraded significantly due to intra- and inter-channel fiber nonlinearities, polarization-mode dispersion (PMD), and chromatic dispersion In order to deal with those channel impairments, novel advanced techniques in modulation and detection, coding and signal processing are needed This unique book represents a coherent and comprehensive introduction to the fundamentals of optical communications, signal processing and coding for optical channels It is the first to integrate the fundamentals of coding theory with the fundamentals of optical communication

164 citations


Journal ArticleDOI
Ansheng Liu1, Ling Liao1, Y. Chetrit2, Juthika Basak1, Hat Nguyen1, D. Rubin2, Mario J. Paniccia1 
TL;DR: The authors' measurements suggest the integrated chip is capable of transmitting data at an aggregate rate of 200 Gb/s, which represents a key milestone on the way for fabricating terabit per second transceiver chips to meet the demand of future terascale computing.
Abstract: We review recent advances in the development of silicon photonic integrated circuits for high-speed and high-capacity interconnect applications. We present detailed design, fabrication, and characterization of a silicon integrated chip based on wavelength division multiplexing. In such a chip, an array of eight high-speed silicon optical modulators is monolithically integrated with a silicon-based demultiplexer and a multiplexer. We demonstrate that each optical channel operates at 25 Gb/s. Our measurements suggest the integrated chip is capable of transmitting data at an aggregate rate of 200 Gb/s. This represents a key milestone on the way for fabricating terabit per second transceiver chips to meet the demand of future terascale computing.

Journal ArticleDOI
TL;DR: In this article, the state of the art in advanced InP photonic ICs is reviewed for the 1.3-1.6 m wavelength optical fiber optical fiber. And the authors present a survey of the state-of-the-art in InP ICs.
Abstract: InP is an ideal integration platform for optical generation, switching, and detection components operating in the range of 1.3-1.6 m wavelength, which is preferred for data transmission in the most prevalent silica-based optical fiber. We review the current state of the art in advanced InP photonic ICs.

Proceedings ArticleDOI
18 Aug 2010
TL;DR: The growing need for optical interconnect bandwidth in data center networks, and the opportunities and challenges for wavelength division multiplexing (WDM) to sustain the “last 2km” bandwidth growth inside data Center networks are reviewed.
Abstract: We review the growing need for optical interconnect bandwidth in data center networks, and the opportunities and challenges for wavelength division multiplexing (WDM) to sustain the “last 2km” bandwidth growth inside data center networks.

Journal ArticleDOI
Jianjun Yu, Xiang Zhou1
TL;DR: It is shown that high-speed QPSK, 8PSK.
Abstract: We review and summarize several 100G per channel high-capacity transmission systems enabled by advanced technologies such as multilevel modulation format, new low-loss and large effective area fiber, hybrid EDFA/Raman amplification, and digital coherent detection technologies. We show that high-speed QPSK, 8PSK, 8QAM, and 16QAM can all be generated using commercially available optical modulators using only binary electrical drive signals through novel synthesis methods, and that all of these modulation formats can be detected using digital coherent detection. We also show our latest research results on 400 Gb/s and 1 Tb/s per channel by using orthogonal DWDM transmission technologies.

Journal ArticleDOI
TL;DR: The performance of the receiver using a digital backpropagation algorithm with varying nonlinear step size is characterized to determine an upper bound on the suppression of intrachannel nonlinearities in a single-channel system.
Abstract: Coherent detection with receiver-based DSP has recently enabled the mitigation of fiber nonlinear effects. We investigate the performance benefits available from the backpropagation algorithm for polarization division multiplexed quadrature amplitude phase-shift keying (PDM-QPSK) and 16-state quadrature amplitude modulation (PDM-QAM16). The performance of the receiver using a digital backpropagation algorithm with varying nonlinear step size is characterized to determine an upper bound on the suppression of intrachannel nonlinearities in a single-channel system. The results show that for the system under investigation PDM-QPSK and PDM-QAM16 have maximum step sizes for optimal performance of 160 and 80 km, respectively. Whilst the optimal launch power is increased by 2 and 2.5 dB for PDM-QPSK and PDM-QAM16, respectively, the Q-factor is correspondingly increased by 1.6 and 1 dB, highlighting the importance of studying nonlinear compensation for higher level modulation formats.

Journal ArticleDOI
TL;DR: A cascaded optical link for ultrastable frequency dissemination comprised of two compensated links of 150 km and a repeater station is demonstrated paving the way to a wide dissemination of ultra-stable optical clock signals between distant laboratories via the Internet network.
Abstract: We demonstrate a cascaded optical link for ultrastable frequency dissemination comprised of two compensated links of 150 km and a repeater station. Each link includes 114 km of Internet fiber simultaneously carrying data traffic through a dense wavelength division multiplexing technology, and passes through two routing centers of the telecommunication network. The optical reference signal is inserted in and extracted from the communication network using bidirectional optical add-drop multiplexers. The repeater station operates autonomously ensuring noise compensation on the two links and the ultra-stable signal optical regeneration. The compensated link shows a fractional frequency instability of 3 x 10(-15) at one second measurement time and 5 x 10(-20) at 20 hours. This work paves the way to a wide dissemination of ultra-stable optical clock signals between distant laboratories via the Internet network.

Journal ArticleDOI
TL;DR: In this paper, an ultra compact demultiplexing operation for Dense Wavelength Division Multiplexing (DWDM) communication systems using resonant cavity in modified-T Photonic Crystal (PC) structure was achieved with 1nm channel spacing and 0.45nm mean value of bandwidth without using either specific materials or complexities in fabrication process.
Abstract: We propose an ultra compact structure to realize demultiplexing operation for Dense Wavelength Division Multiplexing (DWDM) communication systems using resonant cavity in modified-T Photonic Crystal (PC) structure. To the best of our knowledge, this is for the first time that a PC-based demultiplexer has been achieved with 1 nm channel spacing and 0.45 nm mean value of bandwidth without using either specific materials or complexities in fabrication process. Designs offering improvement of channel spacing and bandwidth of the proposed demultiplexer is our aim in this work. The attained characteristics are approximately in the range of the DWDM communication systems. Accurate resonant cavities have been used in terms of location and size of holes in the proposed structure in order for them to capture desired wavelengths in optical telecommunication range. Our simulations indicate the average amount of crosstalk (Xt) and the average quality factor (Q) to be −21.1 dB and 3488, respectively. Two-dimensional (2D) Finite-Difference-Time-Domain (FDTD) is chosen for simulation of the proposed structure. The footprint of the structure is approximately 536 μm 2 and can be fabricated and integrated densely and easily.

Journal ArticleDOI
TL;DR: A high performance monolithically integrated WDM receiver is fabricated on the SOI platform, with key components comprising a 1 x 32 Si-based AWG and an array of high speed waveguided Ge-on-Si photodetectors to demonstrate 32-channel operation in the L-band.
Abstract: A high performance monolithically integrated WDM receiver is fabricated on the SOI platform, with key components comprising a 1 x 32 Si-based AWG and an array of high speed waveguided Ge-on-Si photodetectors. The optical channel spacing is 200 GHz. This configuration was used to demonstrate 32-channel operation in the L-band, where it is particularly challenging for silicon photonics due to the low absorption coefficient of Ge at L-band wavelengths. Each channel is capable of operating at a data rate of at least 10 Gbps, resulting in an aggregate data rate of 320 Gbps. At a BER of 1 x 10(-11), the WDM receiver showed an optical input sensitivity between -16 dBm and -19 dBm.

Journal ArticleDOI
TL;DR: This work reports the first compact silicon CMOS 1x4 tunable multiplexer/ demultiplexer using cascaded silicon photonic ring-resonator based add/drop filters with a radius of 12 microm, and integrated doped-resistor thermal tuners.
Abstract: We report the first compact silicon CMOS 1x4 tunable multiplexer/ demultiplexer using cascaded silicon photonic ring-resonator based add/drop filters with a radius of 12 microm, and integrated doped-resistor thermal tuners. We measured an insertion loss of less than 1 dB, a channel isolation of better than 16 dB for a channel spacing of 200 GHz, and a uniform 3 dB pass band larger than 0.4 nm across all four channels. We demonstrated accurate channel alignment to WDM ITU grid wavelengths using integrated silicon heaters with a tuning efficiency of 90 pm/mW. Using this device in a 10 Gbps data link, we observed a low power penalty of 0.6 dB.

Proceedings ArticleDOI
04 Nov 2010
TL;DR: In this paper, the authors show that PM-QPSK signal components, after propagating in uncompen-sated fiber links, assume Gaussian distribution, both in linear and non-linear regime, even in absence of ASE noise.
Abstract: We show by simulation that PM-QPSK signal components, after propagating in uncompen-sated fiber links, assume Gaussian distribution, both in linear and non-linear regime, even in absence of ASE noise. After DSP equalization, the statistics of decision variables is also Gaussian.

Journal ArticleDOI
TL;DR: In this article, the impact of bandpass narrowing, crosstalk, insertion loss, and PDL on the DWDM channels is investigated based on experiments and numerical simulations for common data rates and modulation formats.
Abstract: Reconfigurable optical add/drop multiplexers (ROADMs) based on 1 X N wavelength-selective switches (WSS) are evolving to support DWDM networks with higher capacity and increased flexibility in wavelength routing. Different WSS technologies can be employed to provide colorless and steerable functionality for ring, or meshed architectures. Improvements in specifications of WSS modules operating on the 50 GHz wavelength grid have enabled 40 Gb/s transmission rates through extensive ROADM networks. The same ROADMs are also expected to support 100 Gb/s transmission in the near future. In parallel, development of lower-cost WSS technologies is allowing ROADMs to expand into edge networks. In all these network applications, propagation through multiple ROADMs generates transmission penalties for the DWDM channels, which need to be factored into the network design. Such OSNR or Q factor penalties can be induced by passband narrowing, imperfect isolation across the signal bandwidth, insertion loss, PDL, and other effects. The impact of these impairments depend on the transmitter and receiver types (e.g., data rate and modulation format), and on the WSS characteristics (e.g., insertion loss, passband width, shape, isolation magnitude and isolation stopband). Key transmission impairments such as bandpass narrowing, crosstalk, insertion loss, and PDL are estimated based on experiments and numerical simulations for common data rates and modulation formats. Implications of temporal fluctuations during power setting throughout a ROADM network are also discussed.

Journal ArticleDOI
TL;DR: The use of fiber Brillouin amplification (FBA) for the coherent transmission of optical frequencies over a 480 km long optical fiber link is described and the gain and the achievable signal-to-noise ratio (SNR) of FBA is measured and compared to that of the widely used uni-directional Erbium doped fiber amplifiers (EDFA) and to the authors' recently built bi- directional EDFA.
Abstract: We describe the use of fiber Brillouin amplification (FBA) for the coherent transmission of optical frequencies over a 480 km long optical fiber link. FBA uses the transmission fiber itself for efficient, bi-directional coherent amplification of weak signals with pump powers around 30 mW. In a test setup we measured the gain and the achievable signal-to-noise ratio (SNR) of FBA and compared it to that of the widely used uni-directional Erbium doped fiber amplifiers (EDFA) and to our recently built bi-directional EDFA. We measured also the phase noise introduced by the FBA and used a new and simple technique to stabilize the frequency of the FBA pump laser. We then transferred a stabilized laser frequency over a wide area network with a total fiber length of 480 km using only one intermediate FBA station. After compensating the noise induced by the fiber, the frequency is delivered to the user end with an uncertainty below 2 × 10−18 and an instability σy(τ) = 2 × 10−14 /(τ/s).

Journal ArticleDOI
TL;DR: This work shows that the topology of an Arrayed Grating Waveguide Router (AWGR) can be used to perform the demultiplexing, and that the AWGR can be considered as a serial-to-parallel converter followed by a DFT.
Abstract: All-optical OFDM uses optical techniques to multiplex together several modulated lightsources, to form a band of subcarriers that can be considered as one wavelength channel. The subcarriers have a frequency separation equal to their modulation rate. This means that they can be demultiplexed without any cross-talk between them, usually with a Discrete Fourier Transform (DFT), implemented optically or electronically. Previous work has proposed networks of optical couplers to implement the DFT. This work shows that the topology of an Arrayed Grating Waveguide Router (AWGR) can be used to perform the demultiplexing, and that the AWGR can be considered as a serial-to-parallel converter followed by a DFT. The simulations show that the electrical bandwidths of the transmitter and receiver are critical to orthogonal demultiplexing, and give insight into how crosstalk occurs in all-optical OFDM and coherent-WDM systems using waveforms and spectra along the system. Design specifications for the AWGR are developed, and show that non-uniformity will lead to crosstalk. The compensation of dispersion and the applications of these techniques to ‘coherent WDM’ systems using Non-Return to Zero modulation is discussed.

Journal ArticleDOI
TL;DR: It is shown that HEXA not only confirms its theoretical sensitivity advantage over PM-QPSK in back-to-back, but also shows a greater resilience to non-linear effects, allowing for substantially increased span loss margins.
Abstract: Coherent-detection (CoD) permits to fully exploit the four-dimensional (4D) signal space consisting of the in-phase and quadrature components of the two fiber polarizations. A well-known and successful format exploiting such 4D space is Polarization-multiplexed QPSK (PM-QPSK). Recently, new signal constellations specifically designed and optimized in 4D space have been proposed, among which polarization-switched QPSK (PS-QPSK), consisting of a 8-point constellation at the vertices of a 4D polychoron called hexadecachoron. We call it HEXA because of its geometrical features and to avoid acronym mix-up with PM-QPSK, as well as with other similar acronyms. In this paper we investigate the performance of HEXA in direct comparison with PM-QPSK, addressing non-linear propagation over realistic links made up of 20 spans of either standard single mode fiber (SSMF) or non-zero dispersion-shifted fiber (NZDSF). We show that HEXA not only confirms its theoretical sensitivity advantage over PM-QPSK in back-to-back, but also shows a greater resilience to non-linear effects, allowing for substantially increased span loss margins. As a consequence, HEXA appears as an interesting option for dual-format transceivers capable to switch on-the-fly between PM-QPSK and HEXA when channel propagation degrades. It also appears as a possible direct competitor of PM-QPSK, especially over NZDSF fiber and uncompensated links.

Book ChapterDOI
01 Jan 2010
TL;DR: In this paper, the authors describe the principle of operation of coherent detection, the concept of the digital coherent receiver, and its performance evaluation, and the challenges for the future are summarized.
Abstract: Coherent optical fiber communications were studied extensively in the 1980s mainly because high sensitivity of coherent receivers could elongate the unrepeated transmission distance; however, their research and development have been interrupted for nearly 20 years behind the rapid progress in high-capacity wavelength-division multiplexed (WDM) systems using erbium-doped fiber amplifiers (EDFAs). In 2005, the demonstration of digital carrier phase estimation in coherent receivers has stimulated a widespread interest in coherent optical communications again. This is due to the fact that the digital coherent receiver enables us to employ a variety of spectrally efficient modulation formats such as M-ary phase-shift keying (PSK) and quadrature amplitude modulation (QAM) without relying upon a rather complicated optical phase-locked loop. In addition, since the phase information is preserved after detection, we can realize electrical post-processing functions such as compensation for chromatic dispersion and polarization-mode dispersion in the digital domain. These advantages of the born-again coherent receiver have enormous potential for innovating existing optical communication systems. In this chapter, after reviewing the 20-year history of coherent optical communication systems, we describe the principle of operation of coherent detection, the concept of the digital coherent receiver, and its performance evaluation. Finally, challenges for the future are summarized.

Journal ArticleDOI
TL;DR: The first 10GHz clock-rate, differential-phase-shift-keyed quantum key distribution system on a 10Gb/s multi-user WDM-PON network is demonstrated and a dual feeder fiber scheme is used to reduce spontaneous Raman scattering-induced inter-channel cross-talk.
Abstract: We present the first demonstration of quantum key distribution (QKD) on a multi-user wavelength division multiplexed passive optical network (WDM-PON) with simultaneous, bidirectional 10Gb/s classical channel transmission. The C-Band QKD system operates at a clock rate of 10GHz and employs differential phase shift keying (DPSK). A dual feeder fiber and band filtering scheme is used to suppress classical to quantum channel cross-talk generated by spontaneous Raman scattering, which would otherwise prevent secure key distribution. Quantum keys were distributed to 4 users with negligible Raman cross-talk penalties. The mean QBER value for 4 users was 3.5% with a mean raw key distribution rate of 1.3Mb/s, which decreased to 696kb/s after temporal windowing to reduce inter-symbol interference due to single photon detector timing jitter.

Patent
10 Jun 2010
TL;DR: In this article, an optical communication system having an optical transmitter and an optical receiver optically coupled via a multi-path fiber is described. But the optical receiver processes the received TMM signal to reverse the effects of inter-mode mixing and recover the data carried by each of the independently modulated components.
Abstract: An optical communication system having an optical transmitter and an optical receiver optically coupled via a multi-path fiber. The optical transmitter launches, into the multi-path fiber, an optical transverse-mode-multiplexed (TMM) signal having a plurality of independently modulated components by coupling each independently modulated component into a respective transverse mode of the multi- path fiber. The TMM signal undergoes inter-mode mixing in the multi-path fiber before being received by the optical receiver. The optical receiver processes the received TMM signal to reverse the effects of inter-mode mixing and recover the data carried by each of the independently modulated components.

Proceedings ArticleDOI
21 Mar 2010
TL;DR: In this article, a coded polarization-multiplexed iterative polar modulation (IPM-IPM) was proposed as an enabling coded-modulation scheme for beyond 400Gb/s serial optical transmission.
Abstract: We propose a coded polarization-multiplexed iterative polar modulation (PM-IPM) as an enabling coded-modulation scheme for beyond 400Gb/s serial optical transmission. We demonstrate that the proposed scheme can achieve 400Gb/s optical transmission over 2250km (for M=3D16).

Journal ArticleDOI
TL;DR: It is demonstrated that the use of a high gain and high output power RSOA as remote modulator enables a 36-dB optical budget for colorless operation at 2.5 Gb/s over 45-km single-mode fiber.
Abstract: We propose a hybrid wavelength-division-multi-plexing/time-division-multiplexing architecture using reflective semiconductor optical amplifiers (RSOAs) for next-generation access solutions. We demonstrate that the use of a high gain and high output power RSOA as remote modulator enables a 36-dB optical budget for colorless operation at 2.5 Gb/s over 45-km single-mode fiber. This RSOA-based configuration provides a reasonable cost per user for this hybrid system and can be easily upgraded.

Journal ArticleDOI
TL;DR: In this article, a single-band self-coherent polarization-multiplexed optical orthogonal frequency-division multiplex system with a raw data rate of 120 Gbit/s is presented.
Abstract: In this paper, we experimentally demonstrate a single-band self-coherent polarization-multiplexed optical orthogonal frequency-division multiplex system with a raw data rate of 120 Gbit/s. The transmitter uses a novel RF structure that eliminates the need for RF mixers and optical filters. The receiver uses a novel architecture where the optical carrier is filtered and amplified for self-coherent detection. The receiver is polarization diverse and allows for the usual frequency guard band between the carrier and the sideband to be reduced in width, thus increasing spectral efficiency. Using two commercial 20 GS/s arbitrary-waveform generators to generate a single information-carrying band per polarization, we achieve a raw data rate of 120 Gbit/s over 500 km of standard single-mode fiber.