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Driven primarily by cloud service and data-center applications, short-reach optical communication has become a key market segment and growing research area in recent years. Shortreach systems are characterized by direct detection-based receiver configurations and other low-cost and small form factor components that induce transmission impairments unforeseen in their coherent counterparts. Innovative signaling and digital signal processing (DSP) play a pivotal role in enabling these components to realize their ultimate potentials and meet data rate requirements in cost-effective manners. This paper presents an overview of recent DSP developments for short-reach communications systems and discusses future trends. [ABSTRACT FROM AUTHOR]

This paper presents the generation and the performance evaluation of optical minimum shift keying (MSK) for high-speed and high-spectral-efficiency wavelength-division multiplexing systems. The detailed principle on optical MSK generation and detection is derived and analyzed. Optical MSK data (10.7 Gb/s) are successfully generated by an experiment using the proposed scheme. The results show that the optical MSK signal exhibits a very compact optical spectrum. The performance of the optical MSK modulated system is evaluated and compared with those of 50% duty-cycle return-to-zero differential phase shift keying (RZ-DPSK) and 50% duty-cycle return-to-zero on-off keying (RZ-OOK) modulated systems, via both simulation and experiment, in terms of dispersion tolerance, linear crosstalk, self-phase modulation (SPM) tolerance, stimulated Brillouin scattering (SBS) threshold, optimal receiver filter bandwidth, and optimal link launch power into single-mode fibers and dispersion compensation fibers. Experimental and simulation results show that the MSK signal exhibits the largest tolerance against fiber dispersion and SPM effect as compared with RZ-DPSK and RZ-OOK. Experimental results also confirm the negative penalty against the SPM effect. The SBS threshold of both the MSK and RZ-DPSK systems is more than 10 dB higher than that of the RZ-OOK system. The MSK that is generated with conventional carrier-suppressed return-to-zero (CSRZ) pulses exhibits a narrower optimal optical filter bandwidth but a wider electrical filter bandwidth compared with those of RZ-OOK and RZ-DPSK. The MSK signal that is generated with pure dual-mode pulses has a similar optimum range to RZ-OOK and RZ-DPSK at a high optical signal-to-noise ratio (OSNR) but has a narrower optimal optical filter bandwidth at a low OSNR. The optimum fiber launch power study shows that the MSK signal that is generated using the conventional CSRZ pulses exhibits higher optimum launch power, which agrees with the SPM to- lerance study. [ABSTRACT FROM PUBLISHER]

This article discusses the various schemes for generating typical advanced modulation formats in terms of configuration and cost, and particularly presents some recently proposed configurations for optical data generation with better performance or reduced components, including pulsed multichannel source generation for return-to-zero (RZ)-based WDM application, multichannel dual-mode pulse source for carrier-suppressed RZ (CSRZ)-based WDM application, CSRZ and CSRZ differential phase shift keyed (DPSK) signal generation using a single Mach-Zehnder modulator (MZM) together with an electrical mixer, chirped RZ generation with reduced modulator number, and RZ/CSRZ-DPSK generation using a single dual-drive MZM and optical minimum shift keying (MSK). [ABSTRACT FROM AUTHOR]

In this article we present the details of a generalized multi-protocol label switching controlled wavelength-division multiplexing (WDM) optical network developed under the Optical Network Focused Interest Group (ONFIG) program in Singapore. The WDM network is controlled through a GMPLS control plane that consists of CR-LDP, LMP, and OSPF-TE. We conducted various field trials on the GMPLS-capable WDM optical network testbed with the main focus on distributed storage service application. We developed and evaluated a distributed storage services application on the WDM optical network testbed and demonstrated that incorporating a lightweight data transport protocol with optical network control could be an efficient approach for data-intensive storage applications by exploiting the dynamic connection establishment and backup protection features. [ABSTRACT FROM AUTHOR]

Tunable fibre Bragg grating (FBG)-based reconfigureably non-blocking optical cross connect (OXC) using multi-port optical circulators (MOCs) are proposed and presented. In an FBG–MOC-based OXC, system insertion loss, system differential insertion loss together with OXC dimensions have been analysed and compared with FBG–OC-based OXC structure using three-port optical circulators (OCs). Optical crosstalk in a multiwavlength FBG–OC-based OXC is discussed, and two crosstalk mechanisms, intraband and interband are identified. To compare FBG based OXC with other OXC structures, an analytical model of intraband optical crosstalk is presented. Results show that tunable FBGs based OXCs are attractive OXC schemes as crosstalk level is independent of the number of wavelength channel per fibre. For the worst case the coherent crosstalk is the dominant crosstalk, which is about 20–30 dB higher than the incoherent crosstalk, depending on the sitching state of the cascaded 2×2 OXCs. However, in practical applications incoherent crosstalk is usually dominant, since it is highly unlikely that all the same wavelength-channels will originate from the same optical source. And the crosstalk of FBGs is the dominant crosstalk. Copyright © 2001 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The performance of WDM networks using shortest path routing is studied under wavelength continuous (WC) and non-continuous (NWC) constraints and dynamic traffic loading. Approximate analytical models are presented for the performance studies of such systems. Results of numerical calculations based on these models and simulations are given for different network topologies for the purposes of comparison. These analytical and simulation results are used to study the performance of these WDM networks under dynamic traffic loading. Copyright © 2001 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A simple switchable dual-wavelength Er-doped fiber-ring laser using a fiber Bragg grating (FBG) written in high-birefringence (HiBi) fibers is proposed. Due to the two-peak reflections with orthogonal polarizations of the FBG, the polarization hole-burning effect in the cavity is greatly enhanced. Experimental results show that a stable dual-wavelength laser with very close wavelength separation (0.39 nm) can be generated at room temperature. Furthermore, the FBG in the HiBi fiber offers flexibility for selection of the laser wavelength. By adjusting a polarization controller, the laser can be switched between the stable single- or dual-wavelength lasing operations. [ABSTRACT FROM AUTHOR]

In this paper we propose a new method for the measurement of the relative group delay of WDM components, based on photonic microwave technique using a low frequency (below 1.3 GHz) scalar network analyzer. Experimental results demonstrate that this technique has the advantages of low cost, simplicity, and high accuracy (less than ±1 ps). © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 346–348, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10602 [ABSTRACT FROM AUTHOR]

Presents a study on photonic mixers and image-rejection mixers for optical subcarrier multiplexing (SCM) systems using Mach-Zehnder optical modulators. Discussion on solving of image-frequency problem by use of photonic-image rejection mixer; Evaluation of image-rejection mixer using nonideal system components; Information on the results of the study.

We report the fabrication, characterization and application of extremely short linear-cavity distributed Bragg reflector fibre lasers (DBR-FLs) written in commercial erbium-doped fibres. The DBR-FL has a total length of 7 mm, of which the nominal cavity is 0.4 mm in length, making it the shortest DBR-FL being reported. Two distinct spectral properties are observed: ultra-narrow linewidth and ultra-low polarization beat frequency, which are measured to be 0.22 kHz and 18.9 MHz, respectively. For the former, the FLs find applications in high sensitivity interferometric sensing, optical frequency metrology and coherent optical communications, whereas for the latter, such a low beat frequency is beneficial to the construction of low-cost and simple demodulator electronics for sensor signal demodulation. The relative intensity noise measurement showed that the relaxation oscillation frequency and relative peak are 120 kHz and [?]75 dB Hz[?]1, respectively. The FL exhibited low-noise characteristics, with an intensity noise of [?]107 dB Hz[?]1 at 1 MHz. We demonstrate the use of these extremely short FLs in the construction of an efficiently pumped and serially multiplexed FL sensor array suitable for practical sensing applications. Two array configurations were tested, namely with individual FLs fabricated in short sections of EDF and connected via passive fibres and with all FLs fabricated along a single EDF. [ABSTRACT FROM AUTHOR]