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Optical circuit switching networks have been recognized as a promising solution for inter-datacenter networks. However, for intra-datacenter networks, they may fall short in efficiently provisioning traffic requests due to their relatively coarse-grained channel assignment and special intra-datacenter traffic patterns. Optical time slice switching (OTSS) has been recently proposed as an optical-switching technique that can provide flexible and transparent optical circuits by extending the merit of flex-grid switching to the time domain, thus achieving much finer granularity. As OTSS requires nanosecond speed optical switches which are expensive, it might not be economically viable to make a one-time upgrade for the entire datacenter. Thus, we expect fine-grained OTSS-enabled and coarse-grained flex-grid-enabled optical switching techniques to co-exist in the foreseeable future. In this study, we investigate an OTSS-enabled flex-grid (OTSS-FG) architecture for intra-datacenter networks. For scenarios where traffic flows are given, we develop a Mixed Integer Linear Program to study the optimal bandwidth allocation scheme in an OTSS-FG architecture. When traffic flows are generated in real time, by leveraging machine-learning techniques to detect flow types, we propose a flow-aware bandwidth allocation (FABA) scheme and a dynamic version of FABA, called “D-FABA” scheme. Numerical simulations show that proposed bandwidth allocation scheme can outperform benchmark schemes in terms of average delay and blocking probability.

We report on an electro-absorption modulator (EAM) integrated laser (EML) based real-time 112 Gbit/s (2 × 56.25 Gbit/s) 4-level pulse amplitude modulation (PAM-4) signal transmission in the C-band over 80 km of standard single-mode fiber (SSMF). Various operating conditions of the EAM were investigated to find the optimum driving conditions for PAM-4 modulation. When the EAM reverse bias was set to the inflection point of the transfer curve, which was −2.35 V, we obtained a bit error ratio (BER) of 4 × 10−8, which is well below the forward error correction (FEC) limit. The results demonstrate the feasibility of using EMLs for implementation in PAM-4 transceivers for inter-datacenter interconnection (inter-DCI) applications.

In this paper, we discuss the issues of supporting protection switching in multiple recovery domains (MRDs). In MRDs, dual node interconnection (DNI) between two adjacent domains is essential to provide reliable services for customers whose traffic traverses multiple domains. Existing linear protection switching solutions in packet transport networks, such as multiprotocol label switching—transport profile (MPLS-TP) and Ethernet, support protection of an end-to-end flow between two end nodes in a recovery domain; however, they do not provide DNI capability between two recovery domains. We propose a DNI scheme with linear protection switching technology and analyze its advantages. In the case of a large number of connections affected by a single failure in MRDs protected by linear protection, traffic recovery can be delayed owing to the signaling associated with excessive simultaneous signal fail triggers. We design a collective interconnection message (CIM) scheme that improves the performance of linear protection DNI (LP-DNI) in MRDs and confirms that the CIM mechanism reduces restoration time significantly. By extensive simulations on link and node failures scenarios, we investigate different combinations of LP-DNI and existing ring protection processes to establish the influence of service resiliency in MRDs.

We introduce a scheduling algorithm for all-optical data center switch supporting high throughput and low delay for non-uniform traffic condition. Simulation result shows that our system achieves 100% throughput and shorter delay than existing methods.

A traditional wavelength-division multiplexed (WDM) backbone network with its rigid features is unsuitable for emerging diverse and high bitrate (400 Gb/s, 1 Tb/s) traffic needs. Flexible solutions employ new technologies such as bandwidth-variable optical cross connects (BV-OXC) with liquid crystal (LCoS) wavelength-selective switches (WSS), sliceable bandwidth-variable transponders (SBVT), etc. in a flex-grid network. Flex-grid network operates on variable spectral granularities (e.g., 12.5 GHz), and higher modulation formats (quadrature amplitude modulation). However, a greenfield deployment of flex-grid technologies may not be practical, due to cost of technology and usability. This leads to a brown-field network where both fixed-grid and flex-grid technologies co-exist with seamless interoperability. Thus traditional traffic routing and resource allocation techniques need to evolve in a mixed-grid infrastructure. Our study considers the dynamic routing and spectrum assignment (RSA) problem in a fixed/flex-grid co-existing optical network. It provisions routes for dynamic, heterogeneous traffic, ensuring maximum spectrum utilization and minimum blocking.

We present a simple and effective method for suppressing thermally induced wavelength drift in a widely tunable digital supermode distributed Bragg reflector (DS-DBR) laser monolithically integrated with a semiconductor optical amplifier (SOA). For fast thermal compensation, pre-compensatory currents are injected into the gain medium section of the DS-DBR laser and the SOA. This method can be easily applied to existing commercial tunable lasers, since it is implemented without any modification to manufacturing process. Experimental results exhibit that wavelength stability is noticeably improved to ± 0.01 nm. We also experimentally demonstrate a fast channel-to-channel switching in a wavelength-routed optical switching system employing a 90 × 90 arrayed waveguide grating router (AWGR). The measured switching time is less than 0.81 µs.

In this paper, we examine the impact of photonic frame length to latency and traffic throughput in photonic packet switching scheme with passive optical switches.

All-fiber 6-mode multiplexer composed of two consecutive LP11-mode selective couplers (MSC), two LP21-MSCs and an LP02-MSC is fully characterized by wavelength-swept interferometer technique. The MSCs are fabricated by polished-type fiber couplers coupling LP01 mode of a single mode fiber into a higher-order mode of a few mode fiber. A pair of the mode multiplexers has minimum mode dependent loss of 4 dB and high mode group selectivity of over 15 dB. Mode division multiplexed transmission enabled by the all-fiber mode multiplexers is demonstrated over fiber spans of 117 km employing an in-line multi-mode optical amplifier. 6 modes of 120 Gb/s dual polarization quadrature phase shift keying signals combined with 30 wavelength channels are successfully transmitted.

The effects of carrier phase estimation on IQ mismatch compensation are investigated and compared for coherent MIMO optical receiver. We investigate the impacts of phase IQ mismatch on required optical signal-to-noise ratio (OSNR) for coherent MIMO detection. The impacts of number of modes and analog-to-digital converter (ADC) resolution are also evaluated. The results show that decision-directed carrier phase estimator could compensate significant amount of IQ mismatch without employing additional compensation technique, and relaxes requirement of ADC resolution.

We propose a novel method to drive ultra-large size and high resolution LCD TV with a single-bank data driver scheme without severe image degradation. We could achieve a maximum luminance and uniformity to be 98cd/m2 and 86%, respectively when gray 128 is displayed. This confirms excellent performance because the conventional dual-bank driver scheme achieves the counterparts to be 90cd/m2 and 93%.

All-fiber mode selective coupler (MSC) is comprised of a few mode fiber (FMF) and a single mode fiber (SMF), coupling the LP 01 mode of the SMF to a specific higher-order mode (HOM) of the FMF. In order to achieve high coupling ratio and low insertion loss, phase-matching condition between the LP 01 mode of SMF arm and the HOM of FMF arm should be satisfied. A polished-type MSC is made by getting their cores into intimate contact. Prism coupling with a polished coupler block can measure the effective refractive index of the mode accurately. We propose and demonstrate three kinds of allfiber mode multiplexer that is composed of consecutive MSCs. 4-mode multiplexer can multiplex 4 modes of LP 01 , LP 11 , LP 21 , and LP 02 by cascading LP 11 , LP 21 , and LP 02 MSCs. It is used for MDM transmission of three modes with 120 Gb/s DP-QPSK signals. In order to enhance the signal transmission performance by receiving degenerate LP modes simultaneously, a mode multiplexer to utilize two-fold degenerate LP 11 modes is proposed. It is composed of two consecutive LP 11 MSCs that allows the multiplexing of LP01 mode and two orthogonal LP 11 modes. We demonstrates WDM transmission of 30 wavelength channels with 33.3 GHz spacing, each carrying 3 modes, over 560 km of FMF. 6- mode multiplexer can multiplex 6 modes of LP 01 , LP 11a , LP 11b , LP 21a , LP 21b , LP 02 modes. We demonstrated WDM-MDM transmission with the all-fiber 6-mode multiplexer. In this paper, the manufacturing method and the recent advancements of the all-fiber mode multiplexer based on the MSCs are reviewed. Long-distance mode division multiplexing (MDM) optical signal transmissions with the all-fiber mode multiplexer are experimentally demonstrated.

The 112 Gb/s dual-carrier differential quadrature phase shift keying (DC-DQPSK) optical transceiver, which does not need digital signal processing and coherent detection, is proposed for cost-effective 100G transport solution. In this paper, we describe upgrade schemes of 10 Gb/s-based WDM optical links by adopting 112 Gb/s DC-DQPSK transceiver, while the dispersion of the optical links is compensated 100% at each span. Method of introducing the DC-DQPSK signal into single grid of 100 GHz spaced WDM link is demonstrated. Performance sufficient for error-free operation after forward error correction is achieved over 640 km standard single mode fiber (SSMF) link. In another method, we experimentally investigate the transmission performance with co-propagating 10.7 Gb/s on-off-keying (OOK) signals over 1000 km of SSMF when the dual carriers occupy two channel grids separately. Excellent tolerance to the nonlinearities impacted by the OOK signals and low optical signal-to-noise ratio requirement are verified to demonstrate superior transmission performance in 10 Gb/s-based WDM links.

This paper proposes a new method to predict color information of liquid crystal displays (LCDs) very accurately. Leaked light from black sub-pixels causes errors of the color prediction based on the individually measured RGB color information. We present a new method to remove the bad influence of the light leakage. We prove that this work can calculate the pure colorimetric information regardless of the shapes of opto-electronic transfer function (OETF) of LCDs. Without this technology, average errors of luminance (ΔY) and chromaticity coordinate (Δxy) over 30 colors were 0.58 cd/m2 and 0.04, respectively. When we applied the proposed method, however, average errors of ΔY and Δxy were 0.03 cd/m2 and 0.005, respectively. Experimental results show that our method can extract pure primary color information with extremely low errors.

We propose a behavioral circuit model to estimate transient optical responses of an active-matrix liquid crystal display (AMLCD). We apply it to twisted-nematic, patterned vertical alignment, and in-plane switching AMLCDs to verify our model's universality. To obtain more accurate simulation results, we propose a method to obtain the capacitance–voltage data from natural optical responses. We describe the behavior of all types of AMLCDs by using an analog hardware description language, Verilog-A. We simulate the AMLCD panels by importing the behavioral circuit model in a circuit simulator, Smart-SPICE. The simulation results of the transient optical responses were almost identical to the measurement ones regardless of liquid crystal modes.

Transmission performances of direct detection-based 100-Gb/s modulation formats are investigated and compared for metro area optical networks. The effects of optical signal-to-noise ratio sensitivity, chromatic dispersion, cross-channel nonlinearity, and transmission distance on the performance of differential 8-ary phaseshift keying (D8PSK), differential phase-shift keying plus three-level amplitude-shift keying (DPSK+3ASK), and dual-carrier differential quaternary phase-shift keying (DC-DQPSK) are evaluated. The performance of coherent dual-polarization quadrature phase-shift keying (DPQPSK) with block phase estimation and coherent DPQPSK with digital differential detection are also presented for reference. According to our analysis, all three direct detection modulation formats could transmit a 100-Gb/s signal over several hundred kilometers of a single-mode fiber link. The results also show that DC-DQPSK outperforms D8PSK and DPSK+3ASK, and the performance of DC-DQPSK is comparable to that of coherent DP-QPSK with digital differential detection. The maximum transmission distance of DC-DQPSK is over 1,000 km, which is enough distance for metro applications.

Impacts of in-phase/quadrature-mismatch (IQ-mismatch) in polarization division multiplexed-16 level quadrature amplitude modulation (PDM-16QAM) coherent optical receiver are investigated and the IQ-mismatch compensation by digital signal processing is examined. All the results are compared with those of PDM-quadrature phase shift keying (QPSK) receiver.

A driving waveform for electrophoretic displays with high image quality is proposed. The proposed driving waveform shows good performance compared to the conventional waveforms. By adding two voltage levels, the number of grey levels expanded from 8 to 165. In addition, the average response time improved from 90 to 61 ms.

The feasibility of multicast-capable-reconfigurable optical add/drop multiplexer (MC-ROADM) based on broadcast-and-select switch is experimentally demonstrated. The MC-ROADM can support unicast connection as well as multicast connection, and can provide directionless switching and low insertion loss in path-through channel. We implement fully-reconfigurable multi-degree MC-ROADM based on wavelength selective switch, and evaluate multicasting performances by fully loading 40 × 10 Gbit/s wavelength division multiplexed (WDM) signals. For unicast and multicast operation, measured spectrum and bit-error-rate (BER) show good uniformity and no power penalty. After 1040 km transmission with 25 dB span loss, the measured BER is higher than forward-error-correction (FEC) limit for BER of 10−15.

We compare the performance of a wavelength remodulated wavelength-division-multiplexed passive optical network implemented using Manchester-coded or inverse-return-to-zero (IRZ)-coded signal downstream and non-return-to-zero remodulated signal upstream. We investigate the effects of varying differences between downstream and upstream bit rates on the two coding schemes. When the bit rate ratio of upstream to downstream is less than or equal to 50%, the performance of Manchester coding is better than that of IRZ coding. However, when the bit rate ratio of upstream to downstream is higher than 50%, Manchester code requires appropriate time delay between upstream and downstream signals, whereas IRZ code needs reduced extinction ratio in the downstream signal.

In this paper, we propose and demonstrate a cost-effective technique to upgrade the capacity of dense wavelength division multiplexing (DWDM) networks to a 40 Gb/s line rate using the existing 10 Gb/s-based infrastructure. To accommodate 40 Gb/s over the link optimized for 10 Gb/s, we propose applying a combination of super-FEC, carrier-suppressed return-to-zero, and pre-emphasis to the 40 Gb/s transponder. The transmission of 40 Gb/s DWDM channels over existing 10 Gb/s line-rate long-haul DWDM links, including 40×40 Gb/s transmission over KT’s standard single-mode fiber optimized for 10 Gb/s achieves successful results. The proposed upgrading technique allows the Q-value margin for a 40 Gb/s line rate to be compatible with that of 10 Gb/s. Keywords: Optical communications, 40 Gb/s, optical link, Q-value, modulation format, forward error correction, optical signal-to-noise ratio.

Experimental demonstration of security-improved optical code-division-multiplexed-access (CDMA) scheme based on spectrally encoded incoherent broadband light source with bipolar coding is presented. Incoherent bipolar encoding is achieved with amplified spontaneous emission (ASE) noise of erbium-doped fiber amplifier. We show details of coding scheme and investigate security issues by measuring eye-diagrams and bit-error-rates for various cases. In addition, we present analytical and numerical simulation results for secure transmission of spectrally encoded incoherent optical CDMA signal.

For the first time to our knowledge, we demonstrate a transmission of 37 channels a 64 quadratic-amplitude-modulation (QAM)-coded high-definition television (HD-TV) signal over a fiber-optic millimeter-wave link. The 60-GHz upconverter/downconverter is implemented based on a Gunn oscillator and a nonradiative dielectric waveguide. For the remote delivery of 37 channels of HD-TV signal through 20 km of single-mode fiber, we use a laser diode operating at 1554 nm and an electroabsorption modulator. We evaluate the performances of HD-TV by measuring error vector magnitude and confirm transmission qualities by observing video contents coded with moving picture expert group-2 (MPEG-2).

We propose all-fiber mode multiplexer composed of two consecutive LP11 mode selective couplers that allows for the multiplexing of LP01 mode and two-fold degenerate LP11 modes. We demonstrate WDM transmission of 32 wavelength channels with 100 GHz spacing, each carrying 3 modes of 120 Gb/s polarization division multiplexed quadrature phase shifted keying (PDM-QPSK) signal, over 560 km of few-mode fiber (FMF). Long distance transmission is achieved by 6 x 6 multiple-input multiple-output digital signal processing and modal differential group delay compensated link of FMF. The all-fiber mode multiplexer has considerable potential to be used in mode- and wavelength-division multiplexed transmission. (C) 2015 Optical Society of America

Automatic gain control method in Raman amplifier with multi-wavelength pumping scheme is presented. Monitoring of several channel power and feedback pump control is used in the gain control method. The condition to minimize the gain deviation is investigated by numerical simulation. Two monitoring channels are necessary to confine gain deviation in ±0.2 dB at two pumps C-band Raman amplifier. In the experiment, gain deviation of 1.5 dB is controlled to 0.2 dB at 38/40 channels drop, and fast suppression of transient gain excursion is achieved.

Experimental demonstration of bipolar spectral encoding code-division multiple-access with modified pseudorandom noise codes is presented. Bipolar spectral encoding is achieved with an erbium-doped fiber amplifier amplified spontaneous emission source and arrayed waveguide gratings. The bit-error rate performance of 1.25 Gbps signal transmission over 80 km single mode fiber is measured in a multiple-user environment.

The characteristics of hybrid fiber amplifier (HFA) are investigated. HFA is composed of three stages: short-length EDFA pre-stage, DCF Raman amplifier, and power boosting EDFA. HFA has low noise figure, high output power, and also wide input power dynamic range. Gain control method of HFA is presented experimentally, and the transient gain excursion is suppressed to less than 0.5 dB at 3 dB channel add-drop. HFA can be used as line amplifier in optical transmission link even combined with distributed Raman amplifier due to wide input power dynamic range. The transmission performance of HFA is better than EDFA by more than 1.0 dB of Q-factor in 720 km SMF transmission.