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Lightwave Technology, Journal of

Issue 2 • Date Feb. 2002

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Displaying Results 1 - 20 of 20
  • Effects of filter concatenation for directly modulated transmission lasers at 2.5 and 10 Gb/s

    Publication Year: 2002 , Page(s): 218 - 228
    Cited by:  Papers (21)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB) |  | HTML iconHTML  

    We report computer simulation results of the effects on optical signal quality of passage through a cascade of wavelength division multiplexing (WDM) filters-multiplexers and demultiplexers-for directly modulated lasers with different chirp characteristics. In particular, lasers with transient or adiabatic chirp characteristics at 2.5 Gb/s and 10 Gb/s are investigated, and we find clear differences between the laser types with respect to filter concatenation effects. Filters with an optical bandwidth suitable for a 200-GHz channel-spacing system are considered, and we evaluate the system behavior as a function of laser frequency offset for a fixed number of filters. The reference network architecture used for the simulations is an optically transparent metropolitan scale network in which the WDM signals may be demultiplexed and then multiplexed again at multiple optical network elements. The signal quality is evaluated in terms of a distortion-induced eye-closure penalty as well as the excess attenuation or loss suffered. We find that transient chirp-dominated lasers show a generally symmetric distortion penalty response to laser frequency offset, whereas the response for adiabatic chirp dominated lasers is highly asymmetric. Furthermore, the extinction ratio for the latter class of lasers can be improved, in some cases, by the appropriate offset between laser and filter center frequencies. View full abstract»

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  • Correction to "pump to signal RIN transfer in Raman fiber amplifiers"

    Publication Year: 2002 , Page(s): 316
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (29 KB) |  | HTML iconHTML  

    First Page of the Article
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  • Sensitivity characteristics of long-period fiber gratings

    Publication Year: 2002 , Page(s): 255 - 266
    Cited by:  Papers (155)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB) |  | HTML iconHTML  

    We present a detailed investigation into the sensitivity of long-period fiber gratings (LPFGs) as a function of temperature, strain, and surrounding refractive index, with particular attention to the higher order cladding modes and the possibilities for ultrasensitive sensors. From a general theoretical analysis, we identify a general sensitivity factor which offers new physical insight into LPFG behavior and represents a useful design aid in conjunction with a set of measurand-specific sensitivity factors. Our analysis reveals the existence of turning points in the mode dispersion characteristics at which ultrasensitive operation may be obtained. In an extensive set of coordinated experiments, we verify the theoretical predictions with close agreement and provide demonstrations of the device behavior close to the turning points. Alternative sensor schemes for temperature, strain, and refractive index based, respectively, on measurement of the dual resonance characteristic of the modes and on the transmission characteristics close to the turning points, utilizing higher order modes of the LPFG, are presented. For two variables at least, we record the highest LPFG sensitivities yet reported View full abstract»

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  • Analysis of phase-matching conditions in flexural-wave modulated fiber Bragg grating

    Publication Year: 2002 , Page(s): 311 - 315
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (114 KB) |  | HTML iconHTML  

    Effective refractive indexes of the core mode and various cladding modes of a tapered single-mode step-index fiber were calculated for identifying the cladding modes of phase matching for coupling with the core mode, caused by a prewritten Bragg grating together with an applied flexural wave (microbending) in the tapered region. With these coupling mechanisms, the previously reported reflection wavelength switching could be well interpreted. Between the core mode and a cladding mode, the Bragg grating caused contradirectional coupling and the flexural wave resulted in codirectional coupling of either first- or second-order diffraction. Meanwhile, the period of the acoustic-induced flexural wave was calibrated to be a few hundreds of micrometers. Based on the phase-matching calculations, the relationship between cladding radius and flexural wave period with a chosen wavelength for reflection switching was provided. Such design considerations should be helpful in implementing wavelength switches, based on flexural wave modulation of fiber Bragg grating (FBG), for the applications of wavelength division multiplexing (WDM) fiber communications View full abstract»

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  • Sliding window criterion codes and concatenation scheme for mitigating timing-jitter-induced errors in WDM fiber transmissions

    Publication Year: 2002 , Page(s): 201 - 212
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB) |  | HTML iconHTML  

    We propose a concatenated coding scheme, which effectively reduces bit errors induced by soliton-soliton collisions (SSC) in wavelength division multiplexing (WDM) soliton transmission systems. A block line coding scheme, the sliding window criterion (SWC) code, is developed based on the nature of SSC-induced timing jitter in soliton communications. We show, by simplified collision model simulations, that the SWC code alone can decrease the SSC-induced timing jitter and, by concatenation to a Reed-Solomon (RS) code, improve both the bit rate and the channel spacing capacity in WDM systems. We compare the performance of our scheme both analytically and by simulations with those of various RS codes and concatenated RS-convolutional code used in optical fiber transmission systems, and show that high redundancy (overhead) does not always give better code performance. Finally, by using full simulations, we show that the SWC code is an effective and promising technique for dispersion-managed fiber WDM systems View full abstract»

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  • Polarization mode dispersion detected by arrival time measurement of polarization-scrambled light

    Publication Year: 2002 , Page(s): 229 - 235
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB) |  | HTML iconHTML  

    Polarization mode dispersion (PMD) limits optical fiber capacity. PMD compensators usually minimize the associated eye closure. This measure scales with the square of the differential group delay (DGD) and makes it difficult to detect low DGDs. However, light with a low-speed polarization modulation suffers arrival time variations, in the presence of PMD, that are proportional to the DGD. These are detected by integrating the voltage-controlled oscillator (VCO) input signal of the clock recovery phase-locked loop (PLL). This novel method has been demonstrated for 40 Gb/s nonreturn-to-zero (NRZ) and for 2×40 Gb/s return-to-zero (RZ) polarization division multiplex transmission. PMD detection sensitivities range between 2 ps and 84 fs View full abstract»

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  • Design and analysis of an optical waveguide tap for silicon CMOS circuits

    Publication Year: 2002 , Page(s): 277 - 284
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB) |  | HTML iconHTML  

    A compact low-loss optical tap technology is critical for the incorporation of optical interconnects into mainstream complementary metal-oxide-semiconductor (CMOS) processes. For this work, an effort has been made to establish an optimal integrated optical tap design in terms of optical loss, bandwidth, economy, and process compatibility with multimetal layer CMOS circuits. A new device, which is based on a variation of the multimode interference effect, has been found to be especially promising. Two-dimensional (2-D) and three-dimensional (3-D) simulation results show low excess optical loss (<0.1 dB) for the design, and a nominal 40% (2.2 dB) optical coupling into the CMOS circuitry over a wide range of guide to substrate distances. Simulated tap devices are on the order of 15 [tin in length. Polymer waveguide materials are targeted for tap fabrication due to planarization properties, low cost, broad index control, and poling abilities for modulation-tuning functions. Low-cost silicon CMOS-based processing makes the new tap technology especially suitable for computer multichip module and board level interconnects, as well as for metro fiber to the home and desk telecommunications applications View full abstract»

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  • Optimal design of flat-gain wide-band fiber Raman amplifiers

    Publication Year: 2002 , Page(s): 250 - 254
    Cited by:  Papers (55)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (109 KB) |  | HTML iconHTML  

    We present a novel method for designing multiwavelength pumped fiber Raman amplifiers with optimal gain-flatness and gain-bandwidth performance. We show that by solving the inverse amplifier design problem, relative gain flatness well below 1% can be achieved over bandwidths of up to 12 THz without any gain equalization devices. This constitutes a substantial improvement in gain flatness compared to the existing wide-band optical fiber amplifiers View full abstract»

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  • High power and highly linear monolithically integrated distributed balanced photodetectors

    Publication Year: 2002 , Page(s): 285 - 295
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (186 KB) |  | HTML iconHTML  

    A distributed balanced photodetector with high saturation photocurrent and excellent linearity has been experimentally demonstrated. The maximum linear direct current (DC) photocurrent of 33 mA per branch is equivalent to 66 mA in single-ended photodetectors. A setup for investigating the alternating current (AC) linearity of the receiver is proposed and experimentally demonstrated. The receiver exhibits high AC linearity, even under high power operation. The bandwidth of the receiver remains unchanged when the effective do photocurrent is varied from 1 mA to 21 mA. The distribution of photocurrents was also measured. Device length for optimum radiofrequency performance is calculated and implemented in the design. A correlation between the dark current of the photodiodes and their failure mechanism has been established. Analyzing the failure mechanism, junction diodes are found to be more suitable for high power applications View full abstract»

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  • Performance evaluation of a new technique for IP support in a WDM optical network: optical composite burst switching (OCBS)

    Publication Year: 2002 , Page(s): 154 - 165
    Cited by:  Papers (65)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (289 KB)  

    The optical composite burst switching (OCBS) technique is proposed to be implemented in an all-optical backbone network to support Internet protocol (LP) traffic. The OCBS is based on two main features. First, several IP packets are assembled in a single macropacket, called burst. Second, the burst contention in an optical switch is handled by means of two techniques, the wavelength dimension and the burst-dropping (BD) technique. Different from traditional optical burst switching, where an entire burst is discarded when all of the output wavelengths are engaged at the arrival instant of the burst, a switch adopting the BD technique discards only the initial part of a burst finding all of the engaged output wavelengths while forwarding the final part of the burst, beginning at the instant in which one wavelength becomes free. The OCBS allows an increase in the switch throughput in terms of number of accepted IP packets because a burst contains a given number of IP packets. We introduce the analytical model that allows us to evaluate the effectiveness of the technique and, in particular, the obtained saving; furthermore, a sensitivity analysis of the saving, with respect to both the optical burst switch parameters and the traffic load, is carried out View full abstract»

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  • 40-Gb/s optical 3R regenerator using electroabsorption modulators for optical networks

    Publication Year: 2002 , Page(s): 195 - 200
    Cited by:  Papers (48)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (143 KB) |  | HTML iconHTML  

    A 40-Gb/s optical retiming, reshaping, and retransmitting (3R) regenerator was proposed and demonstrated using wavelength converters based on electroabsorption (EA) modulators for effectively implementing 40-Gb/s-based or higher bit rate wavelength division multiplexing (WDM) optical networks. The proposed optical 3R regenerator is configured in a very simple architecture, consisting of two wavelength converters, a clock recovery section, and an optical clock generator section. Furthermore, the stable and polarization-insensitive operation, as well as simple adjustment of an optimal operation condition of our proposed optical 3R regenerator, were confirmed by conducting transmission experiments. To investigate the applicability of optical 3R regenerators to optical networks, it was evaluated by insertion between two 500-km-long segments of transmission line. A Q-factor improvement of about 1.5 dB was obtained after transmission over 1000 km, compared to evaluation without the regenerator. This type of optical 3R regenerator proves extremely useful in future high-speed and scaleable all-optical networks View full abstract»

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  • Temperature and vibration insensitive fiber-optic current sensor

    Publication Year: 2002 , Page(s): 267 - 276
    Cited by:  Papers (68)  |  Patents (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (257 KB) |  | HTML iconHTML  

    A robust interferometric fiber-optic current sensor with inherent temperature compensation of the Faraday effect is presented. Sensor configurations based on Sagnac and polarization-rotated reflection interferometers are considered. The sensing fiber is residing and thermally annealed in a coiled capillary of fused silica. The capillary is embedded in silicone within a ring-shaped housing. It is theoretically and experimentally shown that the temperature dependence of the birefringent fiber-optic phase retarders of the interferometers can be employed to balance the temperature dependence of the Faraday effect (0.7×10-4/°C). Insensitivity of the sensor to temperature within 0.2% is demonstrated between -35°C and 85°C. The influence of the phase retarders on the linearity of the sensor is also addressed. Furthermore, the sensitivity to vibration of the two configurations at frequencies up to 500 Hz and accelerations up to 10 g is compared. High immunity of the reflective sensor to mechanical perturbations is verified View full abstract»

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  • Spectral functional forms for gain and noise characterization of erbium-doped fiber amplifiers

    Publication Year: 2002 , Page(s): 243 - 249
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (125 KB) |  | HTML iconHTML  

    We have, for the first time, experimentally verified the black box model based upon the knowledge in the form of characteristic tilt functions and demonstrated accurate characterization of erbium-doped fiber amplifiers (EDFAs) in wavelength division multiplexing (WDM) system operation View full abstract»

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  • Beat interference penalty in optical duplex transmission

    Publication Year: 2002 , Page(s): 213 - 217
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (98 KB) |  | HTML iconHTML  

    The near- and far-end source spectra in optical full duplex systems can heterodyne, producing a high level of beat interference noise in the receiver bandwidth. This is called coherent common-channel crosstalk, the penalty from which is found in addition to that from incoherent near-end crosstalk (NEXT) quantified in an earlier publication. We find most directly modulated high-chirp laser systems, such as those using single-mode distributed feedback lasers or multimode Fabry-Perot (FP) lasers, are relatively immune to coherent NEXT for speeds up to 100 Mb/s. In the transform limit, however, which occurs at high bit rates or low chirp, the maximum allowable NEXT must be decreased by as much as 20 dB, compared to the incoherent case. One solution is to use uncooled single-mode lasers separated by a small wavelength spacing (20 nm, for example) as popularized for the coarse wavelength division multiplexing (WDM) grid View full abstract»

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  • OTDM transmitter using WDM-TDM conversion with an electroabsorption wavelength converter

    Publication Year: 2002 , Page(s): 236 - 242
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB) |  | HTML iconHTML  

    An all-optical multiplexing technique using wavelength division multiplexing (WDM)-time division multiplexing (TDM) conversion with an electroabsorption wavelength converter has been proposed and demonstrated. The effectiveness of this WDM-TDM conversion technique for various pulsewidth settings was experimentally investigated. The fluctuation of the signal performance, which was inevitably caused by the coherent crosstalk between adjacent pulses in the conventional optical time division multiplexing (OTDM) technique, were successfully suppressed, even in the case of wide pulse duration. High Q-factor performance has been maintained for a wide range of duty ration from 36% to 74%. By introducing this technique to the optical time division multiplexer, a highly stable and high-quality 40-Gb/s optical signal can be effectively produced without generating the short pulse or setting two tributaries at orthogonal polarization states, and without introducing high-speed electronics for signal multiplexing. The WDM-TDM conversion with an electroabsorption wavelength converter was extended to 60-Gb/s operation by using three 20-Gb/s tributaries. A clear eye opening was confirmed for a waveform after the WDM-TDM conversion of the 60-Gb/s signal View full abstract»

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  • Bidirectional optical cross connects for multiwavelength ring networks using single arrayed waveguide grating router

    Publication Year: 2002 , Page(s): 188 - 194
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (165 KB) |  | HTML iconHTML  

    Bidirectional optical cross connects (BOXCs) using a single arrayed waveguide grating router and tunable fiber Bragg gratings (FBGs) have been proposed for multiwavelength bidirectional WDM ring networks. Two types of structures in fold-back and loop-back configurations have been considered and their feasibility has been demonstrated experimentally. The performances of two proposed structures have been investigated and compared in terms of crosstalk characteristics and backscattering suppression capability. The performance of the fold-back configuration is less vulnerable to the crosstalk of the arrayed waveguide grating (AWG) router. On the contrary, the BOXCs in loop-back configuration suppress backscattered signals effectively without using optical bandpass filters and, thus, have good scalability and are more cost effective. Therefore, the choice between two structures will depend on the crosstalk requirement in the BOXCs and the characteristics of the AWG router. In transmission of 2.5-Gb/s signals, the power penalty of 0.5 dB has been observed at BER of 10-9 in both structures. Expansion of the proposed 2×2 structure to N × N adopting multistage structure has been discussed. The limitation on the maximum scale due to spectral bandwidth narrowing has been considered View full abstract»

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  • Architectural design for multistage 2-D MEMS optical switches

    Publication Year: 2002 , Page(s): 178 - 187
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (258 KB)  

    Next-generation wavelength routing optical networks requiring optical cross connects (OXC) in the network have the ability to direct optical signals from any input interface to suitable output interfaces by configuring their internal embedded optical switch matrices. Microelectromechanical systems (MEMS) switches are regarded as the most promising technology to achieve such functionality. We consider the construction of a multistage MEMS switch network with single two-dimensional (2-D) MEMS switch blocks. A power loss model is developed that calls on a single MEMS block that is then used to develop the model for a three-stage Clos network. An effective model for maximum loss difference between calls is also developed. Based on these, the paper also proposes three connection patterns [Max + Min greedy (MMG), compressed extended generalized shuffle 1 (C-EGS-1), and compressed extended generalized shuffle 2 (C-EGS-2)] to connect outlet ports and inlet ports between two neighboring stages in a three-stage Clos network. These connection patterns are proved to be optimal and efficient enough to reach the minimums of both the maximum power loss of calls and the maximum loss difference between calls View full abstract»

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  • Multirate optical fast frequency hopping CDMA system using power control

    Publication Year: 2002 , Page(s): 166 - 177
    Cited by:  Papers (43)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (354 KB) |  | HTML iconHTML  

    This paper addresses the problem of real-time multimedia transmission in fiber-optic networks using code division multiple access (CDMA). We present a multirate optical fast frequency hopping CDMA (OFFH-CDMA) system architecture using fiber Bragg gratings (FBGs). In addition, we argue that, in multimedia applications, different services have different quality of service (QoS) requirements; hence, the user only needs to use the minimum required power to transmit the signal, such that the required signal-to-interference ratio (SIR) is met. We show that a variable bit rate optical communication system with variable QoS can be implemented by way of power control with great efficiency. Present-day multirate optical CDMA systems concentrate on finding the code structure that supports a variable rate system, neglecting the importance of the transmission power of active users on the multiple access interference (MAI) and, therefore, on the system capacity. We assign different power levels to each rate through a power control algorithm using variable optical attenuators, which minimizes the interference and, at the same time, provides variable QoS constraints for different traffic types. Although we are using a code family that preserves good correlation properties between codes of different lengths, simulations show a great improvement in the system capacity when power control is used View full abstract»

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  • Numerical analysis of propagation and impedance matching in 2D photonic crystal waveguides with finite length

    Publication Year: 2002 , Page(s): 304 - 310
    Cited by:  Papers (24)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (207 KB) |  | HTML iconHTML  

    A novel way of approaching wave propagation in two-dimensional (2-D) photonic crystal guides with finite length is presented. It is shown that the main propagation features can be captured by borrowing simple concepts of propagation in transmission lines and combining them with other concepts taken from the theory of periodic structures View full abstract»

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  • Synthesis of direct-coupled-resonators bandpass filters for WDM systems

    Publication Year: 2002 , Page(s): 296 - 303
    Cited by:  Papers (78)  |  Patents (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (171 KB) |  | HTML iconHTML  

    A simple technique for the exact synthesis of selective bandpass filters for wavelength division multiplexing (WDM) systems is presented. The filters consist of direct-coupled ring resonators or cascaded Bragg gratings. The proposed technique permits the calculation of the physical dimensions of the optical structures given the desired frequency response of the filter in terms of bandwidth, free spectral range, out-of-band rejection, and frequency characteristic. The technique, explained in detail for Butterworth and Chebyshev frequency responses, is exact, uses closed-form formulae, and is physically well based. The resulting devices are very compact, have a high out-of-band attenuation, and are suitable for high-density integrated optics. Several filters for applications such as channel add-drop, channel selection, demultiplexing, multichannel filtering, and interleavers are designed, analyzed, and discussed in the 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