Search

High speed imaging with improved resolution and wide area scanning are the ultimate targets for designing a MEMS mirror based LiDAR. Simultaneous improvements of above parameters are critical and yet pose design tradeoff among system complexity, cost and compatibility. Here, we propose a high resolution LiDAR for wide area scanning with improved frame rate by allowing minimum design constrains. Extended area scanning is achieved by simplified transmitter design with off-the-shelf low cost optics such as a beam splitter cube and a plane mirror. In addition, an effective scanning strategy is applied to improve the imaging speed for the extended coverage area, which involves sub-pixel imaging of selectively and sequentially shined target areas. Then, a high resolution image can be reconstructed after merging all the sub-pixel values. The proposed architecture is experimentally demonstrated to reconstruct a high resolution image of 1020 × 500 pixels at the fast refresh rate of 20 fps in extended FoV 52° × 26°. The system is also characterized in terms of linearity of extended optical angles, intensity distribution of light beam profile at several angular positions, and quality of scanned objects in the high resolution reconstructed image.

We propose an injection locked triple contact Fabry–Perot laser diode (TC F–P LD) for an uncooled wavelength division multiplexing systems. By controlling injection currents to three electrodes of the TC F–P LD, we are able to tune the cavity mode for an optimum injection locking without using temperature control. Then, we transmitted 20-Gb/s/channel quadrature phase shift keying signal using the LD as either an optical carrier or a local oscillator. We identified contributions of the performance degradation as: 1) intensity noise resulting from a finite common mode rejection ratio associated with a relative intensity noise and 2) decrease of the effective LO power for coherent detection. Finally, we show the uniform bit error rate performance with change of the injection wavelength by 2.8 nm. This is corresponding to 28 °C change of operating temperature.

We investigate feed forward noise suppression for ASE-seeded WDM systems in relation to its limitations. In particular, limitation factors such as background ASE of reflective light sources and filtering effect are thoroughly investigated. We also measure the penalty induced by feed forward parameter variation from the designed value. Although the BER performance is improved by noise suppression, the statistical noise distribution change reduces the effectiveness of noise suppression.

We investigate the impact of noise distribution on the bit error rate (BER) in a WDM system seeded by a spectrum sliced amplified spontaneous emission. The Gamma distribution of the intensity noise was considered for accurate estimation of transmission performance in a real system. The power penalty by the relative intensity noise and the extinction ratio (ER) were calculated to identify a suitable operation range. To consider the finite ER, numerical simulation was conducted. We also investigate change of the noise distribution after noise suppression and fiber transmission, and the effect on the BER by the distribution change.

This paper presents a mean-square deviation (MSD) analysis of the periodic affine projection algorithm (P-APA) and two update-interval selection methods to achieve improved performance in terms of the convergence and the steady-state error. The MSD analysis of the P-APA considers the correlation between the weight error vector and the measurement noise vector. Using this analysis, it is verified that the update interval governs the trade-off between the convergence rate and the steady-state errors in the P-APA. To overcome this drawback, the proposed APAs increase the update interval when the adaptive filter reaches the steady state. Consequently, these algorithms can reduce the overall computational complexity. The simulation results show that the proposed APAs perform better than the previous algorithms.

We propose a theoretical model of reflective modulators for a seeded dense wavelength-division multiplexing (DWDM) system based on amplified spontaneous emission light. A travelling-wave amplifier model is modified to take into account the finite front-facet reflectivity. The net gain and phase shift are updated at every round trip of the cavity to have complex gain for the injected field. With the proposed model, we calculate side-mode suppression ratio, gain, relative intensity noise suppression as a function of injection power, and wavelength detuning for antireflection-coated Fabry-Perot laser diodes. We also investigate the performance of the seeded DWDM system by using the model. The simulation results match well with the experimental results.

Flexible polymer waveguide with a Bragg reflection grating is incorporated to form an external cavity laser with a wide tuning range, and it is evaluated as a tunable light source for wavelength division multiplexing optical communication systems. The highly elastic property of polymer materials makes them suitable for producing a tunable Bragg reflector controlled by an imposed strain. The flexible tunable Bragg reflector is installed on a compact moving stage 6 connected to a piezoelectric motor. By applying a total strain of 60680 μe (6.07%), wavelength tuning of 82 nm is achieved with a side-mode suppression ratio of 43 dB and a linewidth less than 0.1 nm. The tunable laser controlled by a microactuator exhibits long-term stability with a wavelength fluctuation of less than 0.1 nm. In the optical transmission experiment, various wavelengths are used to transmit the 2.5 Gb/s signal over 50 km, excellent performance was observed with a power penalty of 1 dB compared to the DFB laser.

An approach for scheduling the step sizes of an adaptive filter using the affine projection algorithm (APA) is proposed so that its mean-square deviation (MSD) learning curve can be guided along a pre-designed trajectory. This approach eliminates the parameter-tuning process and does not require estimating unmeasurable stochastic quantities. Furthermore, a step-size lower bound is derived in random-walk-modeled environments that leads the adaptive filter to achieve the smallest steady-state MSD, while in stationary environments, the closer to zero the step size is, the smaller the steady-state MSD. For efficient memory usage in practice, the schedule is modified from full-table step sizes to a few down-sampled step sizes without performance degradation. In a simulation, the scheduled-step-size APA exhibits fast convergence and produces small steady-state error not only for a white signal but also for various colored input signals for a properly chosen projection order. The proposed algorithm also demonstrates greater robustness over different signal-to-noise ratios than the existing variable-step-size APAs.

This letter describes how to set up the step size of the affine projection algorithm (APA) based on mean-square deviation analysis. The analysis considers the cross-correlation between the current weight error vector and the prior measurement noises associated with the reused inputs vectors for better prediction of the learning behavior of the APA. With the predetermined step size based on the analysis, the proposed approach eliminates the parameter-tuning process and the derived algorithm achieves both the fast convergence rate and the low steady-state error. Simulation results show that the proposed algorithm performs better than previous algorithms.

This paper presents an improved mean-square deviation (MSD) analysis of the standard affine projection algorithm (APA) based on two distinctive features. First, the propagation model of the error covariance includes the cross-correlation between the current weight error vector and the prior measurement noises associated with the reused inputs; such a cross-correlation has merely been considered previously. Second, the analysis based on n most recent accumulated iterations, rather than a typical analysis based on a current single iteration, is suggested to reveal a previously unseen phenomenon, where n denotes the tap-length of the filter. Simulation results are in better agreement with the proposed theoretical results, than the previous theoretical ones, over a wide range of parameters such as tap-length, projection order, and step-size.

In this paper, the temperature dependence of the gain and saturation power of injection seeded Fabry-Perot laser diodes/reflective semiconductor optical amplifiers are analyzed theoretically and experimentally. For a constant gain, the saturation power increases with the ambient temperature. This dependency explains the observed variation in relative intensity noise versus injection power, as a function of temperature.

We propose and demonstrate a seamless evolution method with protection capability for next-generation (NG) access networks. Both a time-division-multiplexing passive optical network (TDM-PON) and a wavelength-division-multiplexing (WDM-PON) can be accommodated in the same fiber infrastructure and failures of feeder fibers and distribution fibers are protected for each service. Remote reconfigurations of the remote node (RN) for protection and/or evolution can be achieved within 48 ms by instantaneous optical powering at the central office (CO) while maintaining the RN in a passive state.

We derived a theoretical model of a wavelength-locked Fabry-Perot laser diode (F-P LD) to a sliced spectrum of externally injected amplified spontaneous emission (ASE) from wave equations. The model explains the dynamics of the wavelength-locked F-P LD. Using this model, we investigated the noise characteristics of a wavelength-locked F-P LD with respect to the various parameters, such as, the injected ASE power, the bias current of F-P LD, and the wavelength detuning. We also investigated intensity noise increment by spectral filtering in optical access networks based on wavelength-locked F-P LDs.

We derived analytic expression for the relative intensity noise (RIN) of a wavelength-locked Fabry-Perot laser diode (FP LD) in a single mode region. The RIN of the wavelength-locked output is a function of the photon density and the photon life time. It also depends on the wavelength detuning and the injected amplified spontaneous emission (ASE) power. We investigated the modulation transfer function of the wavelength-locked FP LD and its dependence on wavelength detuning. The analytic result has good agreement with the simulation result.

We demonstrate a bidirectional long-reach 64-channel dense wavelength division multiplexing passive optical network (DWDM-PON) based on wavelength-locked Fabry-Peacuterot laser diodes (F-P LDs) with 50-GHz channel spacing. The mode control of the F-P LDs enhances the output power and decreases the required injection power. Packet-loss-free transmission in both 64 upstream and 64 downstream channels is obtained, guaranteeing more than 100 Mb/s per channel through 70 km of single mode fiber without the need for an optical amplifier. The demonstrated DWDM-PON can consolidate a metro network into an access network by bypassing the central offices within its reach. The capacity of the long-reach DWDM-PON is also discussed

Traffic patterns in access networks have evolved from voice- and text-oriented services to video- and image-based services. This change will require new access networks that support high-speed (> 100 Mb/s), symmetric, and guaranteed bandwidths for future video services with high-definition TV quality. To satisfy the required bandwidth over a 20-km transmission distance, single-mode optical fiber is currently the only practical choice. To minimize the cost of implementing an FTTP solution, a passive optical network (PON) that uses a point-to-multipoint architecture is generally considered to be the best approach. There are several multiple-access techniques to share a single PON architecture, and the authors addressed several of these approaches such as time-division multiple access, wavelength-division multiple access, subcarrier multiple access, and code-division multiple access. Among these multiple techniques, they focus on time-division multiplexing (TDM)-PON and wavelength-division multiplexing (WDM)-PON, which will be the most promising candidates for practical future systems. A TDM-PON shares a single-transmission channel with multiple subscribers in time domain. Then, there exists tight coupling between subscribers. A WDM-PON provides point-to-point optical connectivity using a dedicated pair of wavelengths per user. While a TDM-PON appears to be a satisfactory solution for current bandwidth demands, the combination of future data-rate projections and traffic patterns coupled with recent advances in WDM technology may result in WDM-PON becoming the preferred solution for a future proof fiber-based access network

This paper describes a fully integrated zero-IF receiver for cellular CDMA and GPS applications. The single-chip zero-IF receiver integrates the entire signal path for CDMA and GPS bands, including a low-noise amplifier (LNA), I/Q down-converters, baseband channel selection filters (CSFs), a voltage-controlled oscillator (VCO), and a local oscillator (LO) distribution circuit for each band. The cellular-band LNA achieves a noise figure (NF) of 1.2 dB, input third-order intercept point (IIP3) of 11 dBm, and gain of 15.5 dB. Cellular I/Q down-converter and baseband circuitries show 9-dB composite NF, 9 dBm IIP3 and 60-dBm input second-order intercept point (IIP2) without IIP2 calibration. The measured LO leakage is less than -110 dBm at LNA input. The phase noise of the cellular VCO is -134 dBc/Hz at 900-kHz offset with 1.76-GHz carrier frequency. Total GPS signal path achieves NF of 1.7 dB and gain of 74 dB with 42-mA current. The receiver is fabricated in a 0.35-mum SiGe BiCMOS process and packaged in a 6 mm times 6 mm 40-pin micro-lead-frame. Handset measurements report that the receiver meets or exceeds all of the CDMA-2000 requirements

It is anticipated that more than 75 Mb/s per subscriber is required for the convergence service such as triple-play service (TPS). Among several types of high-speed access network technologies, wavelength-division-multiplexing passive optical network (WDM-PON) is the most favorable for the required bandwidth in the near future. Furthermore, WDM technologies, such as athermal arrayed-waveguide grating (AWG) and low-cost light source, have matured enough to be applied in the access network. In this paper, the authors propose and implement a WDM-PON system as a platform for TPS. The system employs an amplified spontaneous emission (ASE)-injected Fabry-Pe/spl acute/rot laser diode scheme. It has 32 channels of 125 Mb/s and adopts Ethernet as Layer 2. Multicast and virtual local area network features are used for the integration of services such as Internet protocol high-definition broadcast, voice-over Internet protocol, video on demand, and video telephone. The services were demonstrated using the WDM-PON system.

The low-frequency intensity modulation in optical transmission systems can occurred by optical performance monitoring or dynamic devices such as acoustooptic tunable filters. Using a conventional receiver model, we derived the optical signal-to-noise ratio (OSNR) and Q penalties due to the low-frequency intensity modulation. The penalty is a function of the extinction ratio, OSNR, the modulation index, and the number of pilot-tone signals. The analytic results show good agreement with the experimental results.

We propose a noise suppression method using a feed forward circuit for injection-seeded WDM-PON. The required injection power is reduced by 8 dB by employing the proposed method. We investigate the limiting factors by tracing the relative intensity noise in the injection-seeded WDM-PON. Interplay of two filtering effects determines the net suppression of noise.

Because the diffraction angle is equal or close to 90/spl deg/ in residual stress measurements by neutron diffraction, the luminosity of the device can be increased by expansion of the detection window height without deformation of the diffraction peak. A high luminosity position sensitive neutron detector has been designed and fabricated for measuring residual stress. The detector has a working window of 200 /spl times/ 100 mm/sup 2/. The detector has high efficiency, good position resolution and linearity, small position error and low background counts. The results of the detector characteristics are presented.

We demonstrate a dense wavelength-division-multiplexing passive optical network (DWDM-PON) at 50-GHz channel spacing based on wavelength locked triple-contact Fabry-Perot laser diodes (TC F-P LDs). A transmission distance of 30 km was achieved at 1.25 Gb/s per channel. By controlling injected currents into three electrodes, we can match a lasing mode of the TC F-P LD to an injection wavelength. We also employ a prefilter before amplified spontaneous emission (ASE) injection to enhance the system performance by reducing a filtering effect. The transmission distance was limited by the back scattering. By changing a location of the seed source for upstream signal to the remote node, the transmission distance can be extended up to 60 km.

We propose and demonstrate a seamless maintenance and protection scheme based on remotely reconfigurable remote node. Protection for fiber failures and a centralized optical time-domain reflectometry test for preventive maintenance can be achieved within 90 ms by using instantaneous optical powering at the central office, while maintaining the passive nature of the passive optical network.

We demonstrate 1.25-Gb/s operation at 50-GHz channel spacing and 10-km single-mode fiber, which is based on a wavelength-locked Fabry-Perot laser diode (F-P LD) and an intensity noise suppression by a gain saturation of F-P LD in front of the receiver. The wavelength-locked F-P LD employs the spectrum-sliced incoherent light with narrow bandwidth of 35 GHz. The intensity noise of wavelength-locked F-P LD is suppressed about 6 dB by the F-P LD in the front of the receiver. As a result, the bit-error-rate curves exhibit the error-free performances over the detuning conditions to cover a whole mode spacing period of F-P LD.

We propose a low-cost solution for the intensity noise suppression in the spectrum-sliced Fabry-Perot laser diode (F-P LD), which is achieved by placing an F-P LD at the receiver region. The F-P LD at the receiver region provides the intensity noise suppression of about 10 dB as well as the increase of the received optical power for the spectrum-sliced optical signal. The Q-factor is improved about 5.9 at a data rate of 1.25 Gb/s. As a result, we successfully demonstrate 10-km error-free transmission at 1.25-Gb/s signal with a transmission penalty of less than 0.5 dB. It is also found that the low spectrum-sliced power of -22 dBm achieves the relative intensity noise level of -112.5 dB/Hz, which is almost independent of the operation current.

We propose a novel automatic wavelength control method of a tunable laser for a wavelength-division-multiplexed passive optical network (WDM-PON). By sending a low-power amplified spontaneous emission light generated from a broadband light source (BLS) to a tunable laser through a wavelength-division multiplexer, we match the wavelength of the tunable laser to a peak transmission wavelength of the multiplexer. The deviation of the wavelength of the tunable laser was less than 0.05 nm from the center of the target channel. We demonstrate up to 10-Gb/s transmission in a WDM-PON by using the proposed method. We also show that system impairments induced by the BLS are negligible.

We demonstrated improved performance of a low-noise broadband light source (BLS) based on mutually injected Fabry-Perot laser diodes for a large capacity and high bit-rate wavelength-division-multiplexed passive optical network (WDM-PON). The 3-dB linewidth and relative intensity noise of each mode of the low-noise BLS are improved by radio-frequency modulation, where the frequency was detuned from the fundamental noise peak of the low-noise BLS. Then, a 622-Mb/s WDM-PON was demonstrated. Furthermore, a 1-Gb/s WDM-PON can be realized with Manchester coding at a channel spacing of 100 GHz. Thus, the proposed low-noise BLS can be employed to realize a highly scalable WDM-PON.

We propose a simple and useful method to measure the facet reflectivity in a Fabry-Perot laser diode (LD). The new measurement method does not require information on LD parameters such as threshold current or optical spectrum. The measurement is based on a simple formula that describes the relationship of facet reflectivity and reflection gain with launching the probe beam of a narrow spectral width.

A remotely reconfigurable remote node (RN) for next-generation (NG) access networks is proposed and demonstrated. The RN is remotely reconfigured by instantaneous optical powering at the central office through feeder fiber and maintained in a passive state by employing optical latching switches (OLSs). The feasibility of the proposed RN is demonstrated by investigating the operating conditions of optical powering for the reconfiguration and its nonlinear effect both for time-division-multiplexing passive optical network (TDM-PON) as legacy services and wavelength-division-multiplexing passive optical network (WDM-PON) as NG services. The existence of OLSs for reconfigurability and crosstalk effect between TDM-PON and WDM-PON are negligible on transmission performance.

A novel, reliable wavelength-division-multiplexed passive optical network (WDM-PON) with self-protection capability is proposed. By utilizing the routing characteristics of N x N arrayed waveguide grating, the proposed architecture can provide automatic protection against any fiber cut between central office and optical network unit (ONU). Compared with the conventional schemes, this scheme adopts colorless ONUs, thus leading to a decrease in the costs of operation, administration, and maintenance, as well as the production cost. Without the performance degradation, the proposed WDM-PON scheme can offer a reliable network service. In the experiment, the protection performance was demonstrated in the carrier-distributed 1.25-Gb/s WDM transmission over 20-km single-mode fiber.

We propose an evolution method from a time-division-multiplexing passive optical network (TDM-PON) with a video overlay to a wavelength-division-multiplexing (WDM)-PON as a next-generation access network. In order to establish a smooth evolution path, a single type of three-port wavelength band combiner/splitter (WC) was used at the remote node and optical network terminations. At the central office, a four-port WC was used to combine the TDM-PON, the video overlay, and the WDM-PON. Crosstalk among those signals is negligibly small.

We propose and demonstrate a simple and color-free wavelength-division-multiplexing passive optical network (WDM-PON) using spectrum-sliced Fabry-Perot laser diodes (F-P LDs). Due to its low front facet reflectivity (~0.1%), the F-P LD shows a broadband lasing spectrum and reduced mode partition noise. By utilizing multiple peaks that are separated by the free-spectral range of the cyclic arrayed waveguide gratings, the 16-channel WDM-PON is successfully demonstrated at 155 Mb/s.

We investigate the effects of back-reflection in wavelength-division-multiplexing passive optical networks having an injected seed light for color-free operation of an optical network unit. The back-reflection-induced penalty is reduced as the linewidth of the seed light is increased. The wavelength-locked Fabry-Perot laser diode to an injected spectrum-sliced amplified spontaneous emission light shows a high robustness on the back-reflections, while a coherent seed light exhibits a high-reflection-induced penalty. We also estimate the maximum allowable fiber loss according to the linewidth of the seed light.

We propose and demonstrate a wavelength-division-multiplexed passive optical network by employing double-contact Fabry-Perot laser diodes (F-P LDs) without a seed light injection. To avoid the high mode partition noise at low frequency, we use a binary phase-shift keying as a modulation format at a low relative intensity noise window. An error-free transmission is achieved by compensating a lasing envelope shift due to temperature variation with the double-contact F-P LD.

An efficient evolution method from a time-division-multiplexing passive optical network (TDM-PON) is proposed and demonstrated for a next-generation PON. A single-type three-port wavelength band combiner/splitter enables a simple and efficient evolution of TDM-PON maintaining the current PON infrastructure and wavelength plan. The crosstalk between the TDM-PON and next-generation PON is negligibly small

A bidirectional 80-km-reach 64-channel dense wavelength-division-multiplexing passive optical network with 50-GHz channel spacing based on wavelength-locked Fabry-Peacuterot laser diodes is demonstrated. By changing the position of the broadband light source (BLS) for the upstream channels to the remote node, both the need for a high-power BLS and the power penalties induced by backscattering are overcome. Packet-loss-free transmission is obtained, guaranteeing 125 Mb/s per channel (8-Gb/s capacity in a single direction) without the support of an optical amplifier

We propose a large-capacity hybrid passive optical network (PON) with a wavelength-sharing technique achieved by applying subcarrier multiple access on each single channel of a wavelength-division-multiplexed (WDM) PON. We also use forward-error correction to reduce the effect of optical beat interference noise. We demonstrate three-subchannel sharing in a 100-GHz-spaced WDM-PON to accommodate three times more subscribers simultaneously at a fully dedicated connection rate of 125 Mb/s

We demonstrate color-free operation of a dense wavelength-division-multiplexing passive optical network based on the wavelength-locked Fabry-Peacuterot laser diodes with injection of a low-noise broadband light source (BLS). The color-free operation, i.e., wavelength-independent operation, was obtained at 50-GHz channel spacing with the help of a narrow injection bandwidth of the low-noise BLS. We also demonstrate three-channel upstream transmission with 100-Mb/s Manchester coded data

We propose and demonstrate a new broad-band light source (BLS) for a wavelength division multiplexing-passive optical network (WDM-PON) based on the wavelength locked Fabry-Pe/spl acute/rot laser diodes (F-P LDs). By mutual injection between two antireflection-coated F-P LDs, we realized a broad-band light with a low relative intensity noise. By using the proposed BLS for wavelength locking of the F-P LD, we achieve color-free operation of the optical network termination with Manchester coded data. We also demonstrate a WDM-PON based on the proposed BLS.

We propose a theoretical model of the wavelength-locked Fabry-Pe/spl acute/rot laser diode (F-P LD) to the externally injected narrow-band amplified spontaneous emission. The model explains the dynamics of the wavelength-locked F-P LD. The simulation results with the proposed model show good agreement with the experimental results.

We demonstrate a bidirectional 12-channel wavelength-division-multiplexing passive optical network (WDM-PON) with 50-GHz channel spacing based on wavelength-locked Fabry-Pe/spl acute/rot laser diodes. The maximum transmission length is 30 km including 20 km of feeder fiber and 10 km of distribution fiber. The proposed WDM-PON system can accommodate 80 channels with erbium-doped fiber amplifier-based broad-band light sources. We also propose a few methods for the wavelength-independent operation of an optical network termination.

Clock-frequency component (CFC) is widely used to monitor chromatic dispersion. However, the CFCs extracted by different clock-extraction (CE) methods show different characteristics about dispersion. We compare the CE methods of nonreturn-to-zero signal for chromatic dispersion monitoring. We also compare the ability of the CE methods to detect the optimum amount of dispersion compensation when optical nonlinearity exists. As a result, we find out the efficient CE methods to monitor the optimum amount of dispersion compensation in the real high-speed transmission systems.

We propose and demonstrate a novel wavelength self-managed optical source for access networks. By polarization multiplexing with two Fabry-Pe/spl acute/rot laser diodes, we can largely reduce wavelength and polarization dependence on the injected amplified spontaneous emission (ASE) light. The worst case power penalty incurred by the wavelength detuning can be decreased within 1 dB. We can obtain not only increased signal power and signal-to-noise ratio but also widened operation range. Even though polarized ASE light is used, data transmission is possible using the proposed source. Therefore, the proposed source is very practical to use in low-cost optical wavelength-division-multiplexing access networks.

We demonstrate a bidirectional wavelength-division-multiplexing self-healing ring network for hub/remote nodes with a single strand of fiber. In this network, self-healing can be achieved within 8 ms. The transmission capacity can be doubled in the operating state. We observed the improvement of power penalty due to the spectral filtering in the realized network with 2.5-Gb/s directly modulated signals.

An automatic gain-controlled bidirectional add-drop amplifier (BADA) has been realized by incorporating pump-controlled bidirectional and unidirectional EDFAs. By using the BADAs, we demonstrate a dynamically reconfigurable bidirectional wavelength division multiplexed (WDM) ring network. The BADA enables dynamic add-drops of wavelength-interleaved bidirectional signals and protects surviving signals against the impairments induced by dynamic network reconfigurations.

We demonstrate a high-gain bidirectional amplifier employing the newly proposed bidirectional dispersion compensation technique. We transmit wavelength interleaved 10 Gb/s/spl times/16-channel bidirectional signal over 200 km of single-mode fiber (SMF) with negligible relative intensity noise (RIN)-induced receiver sensitivity penalty. Furthermore, we show a simple fault detection method in bidirectional transmission link by measuring the aggregate signal power at the monitoring port of the amplifier.

We derive analytic expressions of the ultimate capacity-length-product (CLP) of the wavelength-division-multiplexing (WDM) transmission systems and the ultimate node throughput-length-product (NTLP) of the WDM networks limited by the stimulated Raman scattering (SRS). The CLP and the NTLP are proportional to the square root of the system capacity and the node throughput, respectively. However, they are independent of the system capacity and the node throughput when we compensate for the SRS induced power depletion. The CLP increases as we decrease the amplifier spacing. However, there exists an optimum amplifier spacing that maximizes the NTLP. The analytic results agree well with numerical simulation results.

We demonstrated a wavelength-division-multiplexing passive optical network using a multiple section Fabry-Perot laser diode without a seed light. The electrical envelope tuning of the laser enables color-free operation at 1.25 Gb/s with 100-GHz channel spacing. The mode partition noise is mitigated by shifting the signal spectrum.

We demonstrate an all-optical gain-controlled bidirectional add-drop amplifier (BADA) module by using two fiber Bragg gratings (FBG's). The proposed amplifier module could suppress the power fluctuation of the surviving channels within 0.2 dB even when thirteen out of fourteen channels were added or dropped. In addition, there was no degradation in the receiver sensitivity when this module was used for the bidirectional transmission of wavelength-division-multiplexing (WDM) signals.