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Lightwave Technology, Journal of

Issue 8 • Date Aug. 2005

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Displaying Results 1 - 25 of 35
  • [Front cover]

    Publication Year: 2005 , Page(s): c1
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  • Journal of Lightwave Technology publication information

    Publication Year: 2005 , Page(s): c2
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  • Table of contents

    Publication Year: 2005 , Page(s): 2341
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  • On error-correction coding for CDMA PON

    Publication Year: 2005 , Page(s): 2342 - 2351
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    Optical-code-division multiple access (OCDMA) has been investigated as a multiple-access technique for a long time, but so far, it has not reached any practical success. We investigate the performance of low-complexity OCDMA systems with a realistic model of noise and interference; the main limitation of the system is beat noise. To improve the performance, we consider forward-error correction (FEC) and soft decoding using standard error-correcting codes. The achievable error rates are evaluated using simulations and show significant improvement when FEC is used. The results also show that frequency-hopping systems perform better than temporally coded systems when beat noise is taken into account. View full abstract»

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  • Parametric gain in the strongly nonlinear regime and its impact on 10-Gb/s NRZ systems with forward-error correction

    Publication Year: 2005 , Page(s): 2352 - 2363
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB) |  | HTML iconHTML  

    In this paper, we show that the nonlinear parametric gain (PG) interaction between signal and noise is a nonnegligible factor in the design and analysis of long-haul dispersion-managed optical 10-Gb/s on-off keying nonreturn to zero transmission systems operated at small signal-to-noise ratios (OSNRs) such as those employing forward-error correction (FEC) coding. In such a regime, we show that the in-phase noise spectrum exhibits a large gain close to the carrier frequency, which is due to the higher order noise terms accounting for the noise-noise beating during propagation that is usually neglected in the nonlinear Schrödinger equation. With a novel stochastic analysis that keeps such higher order terms, we are able to analytically quantify the maximum tolerable signal power after which PG unacceptably degrades system performance. We verify such an analytical power threshold by both simulation and experiment. We finally quantify the needed extra OSNR, or equivalently FEC coding gain, required when taking PG into account. View full abstract»

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  • Techniques for nonlinearity cancellation into embedded links by optical phase conjugation

    Publication Year: 2005 , Page(s): 2364 - 2370
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    One of the main causes of signal degradation in high-bit-rate transmission systems is the interplay between fiber nonlinear effects and dispersion. Different techniques to compensate nonlinear effects in transmission systems, by using an optical phase conjugator, have been proposed in the literature. In this paper, two different innovative setups allowing nonlinearity cancellation in an embedded link are disclosed. The proposed schemes are simpler than those previously described and strongly improve systems performances. The physical mechanism allowing nonlinearity compensation is depicted, and the effectiveness of the proposed solutions is numerically demonstrated. Moreover a new practical method, useful for performance optimization of systems including a phase conjugator, is presented. Results apply to any bit-rate and modulation format. View full abstract»

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  • Performance predictions and topology improvements for optical serrodyne comb generators

    Publication Year: 2005 , Page(s): 2371 - 2379
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1016 KB) |  | HTML iconHTML  

    Detailed simulations identify which optical components affect the performance of a radio frequency (RF) and optical comb generator based on an optical loop with a phase modulator. The simulations suggest that the topology of the loop can be modified to give a flatter RF spectrum and a greater resilience to fluctuations in the optical phase length of the loop. Furthermore, a method of filtering the laser's output to reduce the noise floor of the RF comb is proposed and verified. The simulations show that the linewidth of the source is critical to good performance, as are the quality of the sawtooth and the short-term phase stability of the loop. However, the amplified spontaneous emission noise (ASE) from the optical amplifier within the loop is relatively unimportant. View full abstract»

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  • Statistical analysis of subcarrier-modulated transmission over 300 m of 62.5-μm-core-diameter multimode fiber

    Publication Year: 2005 , Page(s): 2380 - 2398
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1752 KB)  

    We simulate subcarrier-modulated (SCM) transmission over 300 m of 62.5-μm-core-diameter multimode fiber (MMF) using 1300-nm edge-emitting lasers and 850-nm vertical-cavity surface-emitting lasers (VCSELs) for beam offsets from 0 to 30 μm. We model 81 "worst-case" fibers while scaling their bandwidth according to a differential modal delay (DMD) criterion of 2 ns/km for our analysis at a center wavelength of 1300 nm and a DMD of 4 ns/km for analysis at 850 nm, all in order to ensure that the worst 5% of the MMF is being modeled as per the Gigabit Ethernet standard. We consider SCM carrier frequencies from 1 to 9 GHz at data rates of 1.25 and 2.5 Gb/s. Results show that SCM transmission with eye-opening penalties (EOPs) below 3 dB is achievable at 2.5 Gb/s for both edge-emitting lasers and VCSELs. VCSELs are found to be better suited for center launch than offset launch while edge-emitting lasers are better suited for offset launch at radial offsets of 17 to 23 μm. The region of best performance for VCSELs under offset launch is from radial offsets of 17 to 30 μm at carrier frequencies of 0 to 8 GHz, over which we observed an EOP less than 5 dB, while for edge-emitting lasers we observed a region of best performance from 10 to 25 μm over carrier frequencies from 2.5 to 9 GHz. This means that if interchannel crosstalk was ignored, a theoretical aggregate maximum bit rate for VCSELs of ∼ 7.5 Gb/s should be achieved for three channels using a single offset launch between 17 and 30 μm for a fiber length of 300 m in order to achieve an EOP less than 5 dB for each channel. For edge-emitting lasers, the theoretical maximum is ∼ 5 Gb/s for two channels with each having an EOP of less than 3 dB for transmission over a fiber of length 300 m. We also demonstrate how SCM performance is influenced by the usable average slope (UAS) of the frequency response: a UAS greater than 0.6×10-8 dB/Hz implies severe deterioration of SCM performance. View full abstract»

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  • Noise suppression of incoherent light using a gain-saturated SOA: implications for spectrum-sliced WDM systems

    Publication Year: 2005 , Page(s): 2399 - 2409
    Cited by:  Papers (61)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB) |  | HTML iconHTML  

    In this paper, we present an experimental and numerical study of semiconductor optical amplifier (SOA)-based noise suppression and its relevance to high-channel-density spectrum-sliced wavelength-division-multiplexed systems. We show that the improvement in signal quality is accompanied by spectral distortion, which renders it susceptible to deterioration in the presence of subsequent optical filtering. This phenomenon originates from the loss of intensity correlation between spectral components of the SOA output when the signal spectrum is altered. As a consequence, a design tradeoff is introduced between intensity noise and crosstalk in high-channel-density systems. These adverse effects can be overcome by optimized SOA design, resulting in a significant improvement in signal quality. View full abstract»

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  • Coherent optical MIMO (COMIMO)

    Publication Year: 2005 , Page(s): 2410 - 2419
    Cited by:  Papers (58)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB) |  | HTML iconHTML  

    We present a multiple-input multiple-output (MIMO) optical link based on coherent optics and its ability to exploit the inherent information capacity of multimode fiber. A coherent implementation differs from previous work in optical MIMO by allowing the system to tolerate smaller modal delay spreads, because of a much larger carrier frequency, and yet maintain the necessary diversity needed for MIMO operation. Furthermore, we demonstrate the use of MIMO adaptive equalization to mitigate intersymbol interference when exceeding the bandwidth-length product of the link. The impact of phase noise is studied with numerical simulation. View full abstract»

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  • Impact of the gain saturation dynamics in semiconductor optical amplifiers on the characteristics of an analog optical link

    Publication Year: 2005 , Page(s): 2420 - 2426
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    We evaluate both theoretically and experimentally the gain saturation dynamics of semiconductor optical amplifiers when inserted into an analog optical link. Its impact in terms of radio frequency response, nonlinearity, and noise is investigated. In particular, the frequency response is shown to be a peculiar high-pass filter exhibiting two characteristic frequencies. View full abstract»

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  • Bidirectional higher order cascaded Raman amplification benefits for 10-Gb/s WDM unrepeated transmission systems

    Publication Year: 2005 , Page(s): 2427 - 2433
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    Benefits provided by higher order bidirectional Raman pumping schemes in 10-Gb/s unrepeated wavelength-division-multiplexing transmission systems are experimentally quantified in terms of BER performances at 10 Gb/s. By keeping under control double-Rayleigh-scattering-noise-induced transmission penalties, which can degrade system performance at very high ON-OFF Raman gain, as well as nonlinear propagation effects such as Brillouin scattering, self- and cross-phase modulations, four-wave-mixing, and Raman-induced crosstalks, we show a total unrepeated system reach enhancement up to 3.5 dB with respect to first-order bidirectional pumping. As confirmed by theory, the maximum reach enhancement is mainly limited by pump-to-signal relative intensity noise transfer induced by higher order copumping. View full abstract»

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  • Numerical simulation of nonuniformly time-sampled pulse propagation in nonlinear fiber

    Publication Year: 2005 , Page(s): 2434 - 2442
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    Numerical simulation of pulse propagation in nonlinear optical fiber based on nonlinear Schrodinger equation plays a significant role in the design, analysis, and optimization of optical communication systems. Unconditionally stable operator-splitting techniques such as the split-step Fourier method or the split-step wavelet method have been successfully used for numerical simulation of uniformly time-sampled pulses along nonlinear optical fibers. Even though uniform time sampling is widely used in optical communication systems simulation, nonuniform time sampling is better or even desired for certain applications. For example, a sampling strategy that uses denser sampling points in regions where the signal changes rapidly and sparse sampling in regions where the signal change is gradual would result in a better replica of the signal. In this paper, we report a novel method that extends the standard operator-splitting techniques to handle nonuniformly sampled optical pulse profiles in the time domain. The proposed method relies on using cubic (or higher order) B-splines as a basis set for representing optical pulses in the time domain. We show that resulting operator matrices are banded and sparse due to the compact support of B-splines. Moreover, we use an algorithm based on Krylov subspace to exploit the sparsity of matrices for calculating matrix exponential operators. We present a comprehensive set of analytical and numerical simulation results to demonstrate the validity and accuracy of the proposed method. View full abstract»

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  • Fabrication process and optical properties of perdeuterated graded-index polymer optical fiber

    Publication Year: 2005 , Page(s): 2443 - 2448
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB) |  | HTML iconHTML  

    We proposed a graded-index polymer optical fiber (GI-POF) enabling greater-than-gigabit data transmission in a short reach network by applying a two-step interfacial-gel polymerization process to a perdeuterated polymer material. Using this process, it is possible to fabricate a nearly optimum refractive-index profile with good reproducibility. In this paper, the preparation of a perdeuterated polymethyl methacrylate (PMMA-d8)-based GI-POF utilizing a PMMA cladding is described. This means that the low-loss PMMA-d8 material is used only for the core. Because the cladding transmits only a small fraction of the optical power, a low-loss material is not necessarily required for the cladding. It was verified that the low attenuation of the PMMA-d8 was maintained even if the cladding was composed of hydrogenated PMMA. As a result, a gigabit data transmission over 300 m was achieved by the PMMA-d8-core and PMMA-cladding GI-POF, which was impossible by the conventional PMMA-based GI-POF. View full abstract»

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  • Fiber-coupled in-line heterodyne optical interferometer for minimally invasive sensing

    Publication Year: 2005 , Page(s): 2449 - 2454
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB)  

    In this paper, the first fiber-coupled no-moving-parts scanning heterodyne interferometer design using a single acoustooptic device (AOD) is reported. The design features a high-stability inline reflective architecture with free-space-scanned minimally invasive sensing via a multizone reflective sensor chip. The common path fiber interconnection allows robust remoting of the compact sensing front end. A proof-of-concept sensing experiment measuring voltage-dependent birefringence is successfully conducted using a voltage-controlled nematic liquid crystal (NLC) sensor chip. The system features a 4.69-dB optical loss, a 200-MHz output frequency, and a 1550-nm eye-safe operation wavelength. Applications for the system include any fiber-remoted sensing using the proposed free-space minimally invasive interrogating optical beams. View full abstract»

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  • Silicon waveguide sidewall smoothing by wet chemical oxidation

    Publication Year: 2005 , Page(s): 2455 - 2461
    Cited by:  Papers (54)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    This paper reports a new and more efficient Si waveguide sidewall smoothing process using wet chemical oxidation. Sidewall roughness is a major source of loss and an impediment to realizing high-transmission Si waveguides. The postetch multistepped approach allows for efficient smoothing (in terms of roughness amplitude reduction to material consumption) by continuous oxidation in the fast reaction-limited regime. This method reduces waveguide transmission loss without sacrificing dimensional integrity or thermal budget. In this proof-of-concept work, Si waveguide sidewall loss has been reduced from 9.2 to 1.9 dB/cm. View full abstract»

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  • Efficient nonadiabatic planar waveguide tapers

    Publication Year: 2005 , Page(s): 2462 - 2468
    Cited by:  Papers (14)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB) |  | HTML iconHTML  

    We report taper designs with high transmission efficiencies and with lengths shorter than those needed for adiabatic operation. The tapering occurs between rectangular optical waveguides with the same vertical silicon-on-insulator layer structure, but with different horizontal widths, namely 0.5 and 2.0 μm, and for taper lengths between 0.5 and 3.0 μm. After a comparison between two different optimization methods in a two-dimensional calculation scheme, one of these is repeated using three-dimensional calculations. The results show that, also in the length region where conventional linear and parabolic tapers are not yet adiabatic, tapers with a high efficiency can be designed by applying complex taper structures with more degrees of freedom. View full abstract»

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  • Ferroelectric PVDF cladding terahertz waveguide

    Publication Year: 2005 , Page(s): 2469 - 2473
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    A new type of flexible terahertz-wave hollow waveguide has been developed using ferroelectric polymer poly vinylidene fluoride (PVDF) as the cladding material. The transmission efficiency of the PVDF waveguide was better than a metal hollow waveguide with the same size and structure as the PVDF waveguide. This paper also reports the bent-angle dependencies of the transmission efficiency of the hollow PVDF. View full abstract»

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  • Theory and design of double-cavity Raman fiber lasers

    Publication Year: 2005 , Page(s): 2474 - 2483
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    We introduce the concept of the double-cavity Raman fiber laser (DC-RFL) with three Bragg gratings at the laser wavelength. In such RFLs, the threshold pump power and the conversion efficiency at large pump powers can be designed independently of each other, whereas in ordinary single-cavity RFLs these two optimization criteria collide. The particular behavior of DC-RFLs is interpreted, and a simple technique for the numerical simulation and an analytical relation for the threshold pump power of these devices are presented. View full abstract»

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  • Investigation of room-temperature multiwavelength fiber-ring laser that incorporates an SOA-based phase modulator in the laser cavity

    Publication Year: 2005 , Page(s): 2484 - 2490
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    A theoretical and experimental study of a multiwavelength fiber-ring laser that incorporates a semiconductor optical amplifier (SOA) in the laser cavity as a phase modulator to suppress the homogeneous line broadening is presented. The analysis reveals that the phase shift introduced by the SOA-based phase modulator is more significant than that formed using a LiNbO3 phase modulator, which leads to a better suppression of the homogeneous line broadening. Multiwavelength lasing with small wavelength spacing and improved stability at room temperature is achieved. A fiber-ring laser based on the proposed approach is implemented. Stable multiwavelength operation with up to 26 wavelengths and wavelength spacing as small as 0.19 nm at room temperature is demonstrated. View full abstract»

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  • Theory of spontaneous emission noise in multisection semiconductor lasers

    Publication Year: 2005 , Page(s): 2491 - 2504
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    Calculations of spontaneous emission noise in semiconductor lasers are mainly based on a fundamental theory developed by Henry in 1986, which is useful for simple systems, together with a formulation in terms of transfer matrices by Makino and others, which facilitates application of the theory to more complicated multisection systems. The aim of this review is to present a unified account of this theoretical work in a transparent form intended to encourage its further use in complex systems. The opportunity is taken to strengthen the existing theory by including the effects of differing optical wave vectors in different sections and the consequent reflections at interfaces, which are important in some applications. Sample calculations are presented for a range of systems with one, two, three, and four sections and the predictions compared with other theoretical and experimental results. View full abstract»

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  • Analysis of partially depleted absorber waveguide photodiodes

    Publication Year: 2005 , Page(s): 2505 - 2512
    Cited by:  Papers (12)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB) |  | HTML iconHTML  

    This paper presents the analysis and characterization of partially depleted absorber (PDA) photodiodes. Coupling to these photodiodes is achieved through a planar short multimode waveguide (PSMW) structure. Electric transport in the PDA structure has been investigated and an equivalent electric circuit was developed. Measurements on 5×20 μm2 PSMW PDA photodiodes have shown 0.80 A/W responsivity with a fiber mode diameter as high as 6 μm. The transverse electric/transverse magnetic polarization dependence was <0.5±0.3 dB with -1-dB input coupling tolerances as high as ±2.0 and ±1.3 μm for horizontal and vertical directions. The -3-dB bandwidth was 50 GHz, and the -1-dB compression current at 40 GHz was 17 mA corresponding to +4.5 dBm radio frequency (RF) power. Compared to similar evanescently coupled p-i-n photodiodes, the saturation current has been significantly improved while maintaining comparable bandwidth and high responsivity. View full abstract»

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  • Dynamic regimes in semiconductor lasers subject to incoherent optical feedback

    Publication Year: 2005 , Page(s): 2513 - 2523
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    The dynamics of a semiconductor laser subject to polarization-rotated (incoherent) optical feedback in the long cavity limit has been numerically and experimentally investigated. The results show that the induced dynamics can be grouped into four regimes (stable, chaotic, pulsed, and two state) and that the transverse-magnetic mode of the laser never lases in the ring cavity configuration studied. In addition, unlike the earlier short-cavity work, the boundaries between the regimes in the long-cavity case were found to be independent of the external-cavity delay time. View full abstract»

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  • Influence of pump parameters on two-pump optical parametric amplification

    Publication Year: 2005 , Page(s): 2524 - 2530
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    An analysis of two-pump optical parametric amplifiers is proposed in order to evidence strategies to project and develop flat two-pump fiber parametric amplifiers (2P-OPAs). Amplifier gain profile is evaluated through a model that takes into account the four-wave mixing process with pump depletion. Disturbing influence of degenerate three-wave mixing processes is separately addressed. Through the analysis, important 2P-OPA project guidelines are obtained. Theoretical forecasts are confirmed by experimental measurements on different 2P-OPAs, realized by changing power and spectral allocations of the two pumps, obtained by Raman amplification. View full abstract»

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  • A polymer-dispersed liquid crystal-based dynamic gain equalizer

    Publication Year: 2005 , Page(s): 2531 - 2541
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    This paper presents results obtained with a spatial light modulator (SLM) using a polymer-dispersed liquid-crystal (LC) material to provide dynamic gain equalization (DGE) for wavelength-division multiplexing (WDM) networks. We show the benefit of using a nonchannelized approach to adjust some physical parameters such as the ripple and the maximum obtainable attenuation slope for the spectra to be equalized. Particular attention is paid here to polarization dependence that can result from parasitic anisotropic multiple path interferences as well as induced anisotropy due to a planar transverse field when using a free-space SLM structure. In this frame, we demonstrate an original approach using a depolarizing prism that is only appropriate to such choice of material and that mitigates these effects. Finally, material engineering to widen the operating temperature range is also shortly presented in this paper. View full abstract»

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Aims & Scope

The Journal of Lightwave Technology contains articles on current research, applications and methods used in lightwave technology and fiber optics.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Peter J. Winzer
Alcatel-Lucent Bell Labs