15-GHz modulation bandwidth, ultralow-chirp 1.55-μm directlymodulated hybrid distributed Bragg reflector (HDBR) laser source

A hybrid source has been realized, integrating a fast Fabry-Perot laser and a fiber grating. The device has shown very good performances in the 1530-1570-nm range, obtaining 16 mA of threshold current at 20°C, 1.6-mW fiber optical power and 48 dB of sidemode suppression ratio at 50 mA bias current. The cavity length was designed to achieve a good tradeoff between chirp reduction and increasing speed. The device has shown for the first time, to our knowledge, more than 15 GHz of small-signal modulation bandwidth, and 10-Gb/s modulation capability. Moreover, a penalty-free transmission experiment at 2.5 Gb/s over 100 km of standard fiber has confirmed the very low wavelength chirp of the device. These previous characteristics together with an extremely low temperature dependence (<0.02 nm/°C) make the hybrid distributed Bragg reflector (HDBR) particularly suitable for dense wavelength-division-multiplexing systems     

Applications of 40-Gb/s Chirp-Managed Laser in Access and Metro Networks

We investigate 40-Gb/s cost-efficient transmitter for access and metro networks. This 40-Gb/s transmitter comprises a standard directly modulated distributed-feedback (DFB) laser and a subsequent optical filter. Large dispersion tolerance of this transmitter is realized by chirp control through the phase correlation between adjacent bits for the destructive interference in order to erase the power of “0” bits while enhancing the extinction ratio. The chirp model of the DFB laser and the optimum parameters of the optical filter have been numerically analyzed. The chirp-managed 42.8-Gb/s transmission over 20-km standard single mode fiber (SSMF or SMF-28) without dispersion compensation and a centralized lightwave WDM-PON system are experimentally demonstrated. We have also realized the transmission over 100-m graded index plastic optical fiber (GI-POF). Moreover, the application in the metro network over 240-km SSMF or SMF-28 has also been investigated in this paper.      

Transmission Over 360 km Using a 2.5-Gb/s SOA-Modulator Integrated Full$C$-Band Wavelength-Tunable Transmitter

We present an external-cavity wavelength-tunable laser with a semiconductor optical amplifier-modulator monolithically integrated on the gain chip. The modulator chirp is analyzed, and it is explained how the chirp can be partially cancelled by self-phase modulation in the transmission fiber. Full$C$-band transmission of 2.5-Gb/s data over 360 km is demonstrated with small power penalty.     

Negative-chirp electroabsorption modulator using low-wavelengthdetuning

The negative chirp of an electroabsorption modulator having an α-parameter value of 0 to -0.5, at an input light wavelength of 1.55-1.56 μm, has been developed by optimizing the bandgap energy of an InGaAsP bulk absorption layer. We have demonstrated successful transmission with 10 Gb/s NRZ modulation over a 100-km span of standard fiber without resort to dispersion compensation     

Surface Mountable 10-Gb/s InP Mach–Zehnder Modulator Module for SFF Transponder

We have developed a small, surface mountable InP-based Mach-Zehnder modulator module. New designs for the electrical ports enable the modulator to be directly mounted on a printed circuit board. We demonstrated a 100-km transmission through single-mode fiber with a 10-Gb/s nonreturn-to-zero signal and a 220-km transmission with a 10-Gb/s optical duobinary signal to confirm the applicability of this device as an ultralong-haul small form factor transponder.     

An electroabsorption modulator module for digital and analogapplications

This paper presents an electroabsorption modulator (EAM) module for digital and analog (D/A) applications. Optically broad-band operation of the EAM module is studied for such digital application as wavelength division multiplexing (WDM) systems. Utilizing anisotropic electroabsorption of a multiple quantum-well (MQW) EAM, 40- and 100-nm bandwidth operations in 2.5-Gb/s digital signal transmission over 200-km standard fiber are confirmed by the experiments and the simulations, respectively. For analog applications, low distortion and high link gain characteristics of the EAM module are investigated at the wavelength of 1535 nm. High spurious-free dynamic range of 123 dB·Hz^4/5 and high link gains of -10.3 dB with matching circuit and -20.6 dB without matching circuit are obtained using the EAM module     

80-Gb/s wavelength conversion based on cross-phase modulation inhigh-nonlinearity dispersion-shifted fiber and optical filtering

Using cross-phase modulation in a 1-km high-nonlinearity dispersion-shifted fiber with subsequent filtering by a tunable optical filter, 80-Gb/s pulsewidth maintained wavelength conversion is realized. Penalty-free transmission over 80-km conventional single-mode fiber and 12-km dispersion-compensating fiber for 80-Gb/s converted signal is realized     

Direct intensity modulation in sampled-grating DBR lasers

In this letter, we present new experimental results obtained for direct intensity modulation of widely tunable sampled-grating distributed Bragg-reflector (SGDBR) lasers. These results are of significance to SGDBR applications in wavelength-division-multiplexing systems. The devices described operate in the C-band (wavelength range 1525-1565 nm). A 6-GHz small-signal modulation bandwidth and >10-dB signal extinction ratio under large-signal operation were obtained. We have also recorded an undistorted eye pattern for a nonreturn-to-zero random signal 2³¹-1 word length at 2.5-Gb/s bit rate during transmission over 75-km of standard single-mode fiber     

Design and performance of externally modulated 1.5-μm lasertransmitter in the presence of chromatic dispersion

Key laser and modulator characteristics that impact the use of externally modulated lasers in the presence of chromatic dispersion, excluding effects due to fiber nonlinearities, are reviewed. After a brief consideration of transmission performance with directly modulated 1.5-μm DFB lasers which have limited application of up to 80 km at 2.5 Gb/s, the key design characteristics of externally modulated transmitters are discussed. Experimental results showing the effects of modulator chirp and laser linewidth at a 2.5-Gb/s transmission rate are presented. It is found that lasers with CW linewidth under 100 MHz have less than 2-dB dispersion penalty for 600 km of non-dispersion-shifted fiber. Lower dispersion penalties can be realized if the modulator chirp is tuned so as to narrow the transmitted pulses. Excellent modulator stability is demonstrated for 60 days of error- and degradation-free 2.5-Gb/s operation     

160-gb/s adaptive dispersion equalization using an asynchronous dispersion-induced chirp monitor

This paper describes an adaptive dispersion equalizer (ADE) that uses an asynchronous dispersion-induced chirp monitor and the detailed study of the first demonstration of 160-Gb/s adaptive dispersion equalization. The device successfully equalized the dispersion change over a 40/spl deg/C temperature range (from 5/spl deg/C to 45/spl deg/C) and the dispersion slope of an 80-km dispersion-shifted fiber (DSF). The ADE will enhance the feasibility of 160-Gb/s optical transmission systems.     

Dependence of frequency chirping on bias current in LD wavelength conversion

Chirping influence is experimentally studied in wavelength conversion using a light injected DFB-LD. It is shown that signal degradation due to frequency chirping is small when the bias current is large and the relaxation oscillation frequency is high. An experiment demonstrates that 5-Gb/s wavelength converted light at 1.55 /spl mu/m is transmitted through 160-km nondispersion-shifted fiber with 2-dB penalty, which is only 0.5 dB larger than that in transmission using a LiNbO/sub 3/ Mach-Zehnder modulator.     

Dispersion-Tolerant Millimeter-Wave Photonic Link Using Polarization-Dependent Modulation

A novel technique to modulate one carrier in a dual-carrier millimeter-wave (mm-wave) photonic system is presented and experimentally evaluated. The technique utilizes the polarization dependence of an optical phase modulator and the properties of optical heterodyning and is demonstrated for both amplitude- and phase-modulated mm-wave signal outputs. Experimental verification of the technique is presented with transmission of up to 2.5-Gb/s nonreturn-to-zero data, multilevel quadratic-amplitude modulation, and IEEE 802.11a WLAN data signals on a 40-GHz carrier over optical fiber and wireless transmission. The tolerance for fiber dispersion is investigated, and penalty-free transmission over 44 km is verified. The linearity of the system is evaluated by measuring the spurious-free dynamic range. [All rights reserved Elsevier].     

Bidirectional Transmission Using Tunable Fiber Lasers and Injection-Locked Fabry–PÉrot Laser Diodes for WDM Access Networks

We propose and demonstrate the use of fiber ring lasers and Fabry-Perot laser diodes (FP-LDs) for wavelength-division-multiplexing access networks. The fiber ring laser not only generates downstream data traffic but also serves as the wavelength-selecting injection light source for the FP-LD located at the subscriber site. Moreover, it is wavelength tunable and can be applied to dynamic wavelength assignment networks. The ring laser has a tunable range of 30 nm in the C-band and a power fluctuation smaller than 0.6 dB. For 10-Gb/s downstream and 1.25-Gb/s upstream transmissions over 10-km single-mode fiber, power penalties less than 0.9 and 0.5 dB are demonstrated, respectively. A 40-dB sidemode suppression ratio is obtained for the FP-LD injection-locking at 1544.8 nm.     

Wavelength-independent operation of EA-modulator integratedwavelengthselectable microarray light sources

In this letter, we have simultaneously fabricated five wavelength-selectable microarray light sources (WSLs), each having a different wavelength range integrated with an electroabsorption (EA) modulator on a single wafer. We also introduced a novel device configuration scheme for wavelength-independent modulation. The five EA-WSLs fully covered the entire C-band and had a low uniform threshold current of 6 ± 1 mA at 25°C. Wavelength-independent extinction characteristics were obtained over a tuning wavelength range of 8 nm, and 2.5-Gb/s transmission over 600 km was successfully achieved     

Compensation for chromatic dispersion and nonlinear effect in highdispersive coherent optical repeater transmission system

A design for a chromatic dispersion equalizer that provides 4.4 times higher efficiency in the dispersion compensation characteristics, compared with a conventional equalizer, is proposed. In addition, the amplitude response slope in the frequency domain is less than half of the conventional characteristic. This extends the compensation limit for chromatic dispersion up to 82500 ps/nm for a 2.5-Gb/s heterodyne system, which corresponds to a 4900-km normal dispersion fiber transmission system. A compensation method for modulational instability is also proposed. The method was confirmed by a 2.5-Gb/s continuous-phase frequency-shift-keying (CPFSK) 764-km normal dispersion fiber transmission experiment, with the abovementioned chromatic dispersion equalizer. Employing computer simulations, an over-1000-km normal dispersion fiber optical repeater transmission system with 2.5-Gb/s CPFSK heterodyne detection was shown to be feasible     

Transmission performance of 10-Gb/s 1550-nm transmitters using semiconductor optical amplifiers as booster amplifiers

We have demonstrated the transmission performance of 10-Gb/s transmitters based on LiNbO/sub 3/ modulator using semiconductor optical amplifiers (SOAs) as booster amplifiers. Utilizing the negative chirp converted in SOAs and self-phase modulation induced by high optical power, we can successfully transmit 10-Gb/s optical signals over 80 km through the standard single-mode fiber with the transmitter using SOAs as booster amplifiers. SOAs can be used for booster amplifiers with a careful adjustment of the operating conditions. In order to further understand an SOA's characteristics as a booster amplifier, we model SOAs and other subsystems to verify the experimental results. Based on the good agreement between the experimental and simulation results, we can find the appropriate parameters of input signals for SOAs, such as extinction ratio, rising/falling time, and chirp parameter to maximize output dynamic range and available maximum output power (P/sub o,max/).     

Wide Temperature Range Operation of a 1.55-$mu$m 40-Gb/s Electroabsorption Modulator Integrated DFB Laser for Very Short-Reach Applications

We present the uncooled operation of a 1.55- mum 40-Gb/s InGaAlAs electroabsorption modulator (EAM) integrated distributed-feedback (DFB) laser within a temperature range of 95degC (-15degC to 80degC ). To the best of our knowledge, this is the largest temperature range reported so far for such a 40-Gb/s EAM integrated DFB laser. We designed the EAM to operate at high speed by reducing the electrical parasitics, and we achieved a 3-dB frequency bandwidth of over 39 GHz for an EAM length of less than 150 mum. We demonstrated a 2-km single-mode fiber (SMF) transmission at 40-Gb/s over a wide temperature range of -15degC to 80degC by adjusting only the bias voltage to the EAM while keeping the modulation voltage swing constant at 2.0 V when the temperature changed. We achieved a dynamic extinction ratio of over 8.2 dB and a 2-km SMF transmission with a power penalty of less than 2 dB over a wide temperature range.     

Optical Dispersion Compensator With$&#8811;$4000-ps/nm Tuning Range Using a Virtually Imaged Phased Array (VIPA) and Spatial Light Modulator (SLM)

We present an optical tunable chromatic dispersion compensator based on a virtually imaged phased-array and spatial light modulator providing both positive and negative dispersion. We demonstrate tunable dispersion compensation of 10-Gb/s positively chirped nonreturn-to-zero data signal over a range of$-4080sim+850$ps/nm (240-km single-mode fiber to 9.5-km dispersion-compensating fiber), which operates independent of the input state of polarization and has potential capability for wavelength-division multiplexing.     

25-Gb/s optical NRZ transmission over 40 km of single-mode fiber at 1550 nm without dispersion compensation

We present a method for transmitting 25-Gb/s optical nonreturn-to-zero signals at a wavelength of 1550 nm over a 40-km single-mode fiber without any dispersion compensation methods. We propose optimized self-phase modulation by varying parameters of the fiber launching power and the extinction ratio of optical non-return to zero signals to overcome severe signal distortions by the chromatic dispersion effect. Using the optimization of the self-phase modulation effect, we were able to transmit 25-Gb/s optical nonreturn-to-zero signals over a 40-km single-mode fiber, which can be applicable to passive optical networks with a single wavelength channel and a high split ratio. We demonstrated that the self-phase modulation effect can be controlled by the extinction ratio and the fiber launching power.     

Simultaneous compensation of laser chirp, Kerr effect, anddispersion in 10-Gb/s long-haul transmission systems

The effects of chirp and fiber nonlinearity in a directly modulated 10-Gb/s intensity-modulated direct-detection (IM-DD) fiber transmission system are investigated by simulation, and a simple and flexible technique for compensating these effects is discussed. Self-phase-modulation (SPM) in optical fiber can be equalized by an anomalous dispersion fiber, whereas pulse broadening caused by laser transient chirp can be compensated by normal dispersion. Using these characteristics, laser transient chirp, SPM, and fiber dispersion can be simultaneously compensated by equalizing fibers inserted within certain intervals. Optimum compensation is always realizable for such fixed equalizing fibers, since the magnitude of SPM can be controlled by changing the optical power in the fiber. Simulation suggests that this technique enables 10-Gb/s, 100-km fiber transmission by direct modulation