Theoretical performance of multigigabit-per-second lightwavesystems using injection-locked semiconductor lasers

The locking conditions for multigigabit-per-second modulation are examined, and the dependence of the receiver sensitivity on the fiber dispersion coefficient-length product is investigated. With a 4.8-Gb/s NRZ (nonreturn-to-zero) modulation, a 1-dB penalty in receiver sensitivity occurs for a transmission distance of 68 km. The injected power is 0.4 mW and the frequency detuning is -35 GHz. With 10-Gb/s NRZ modulation, the allowable transmission distance is 12.5 km for an injected power of 1.0 mW and a frequency detuning of -35 GHz. These results represent increases in the transmission distances obtained with a solitary laser by factors of 3.7 at 4.8 Gb/s and 2.7 at 10 Gb/s     

4$,times,$25 Gb/s Frequency-Modulated DBR Laser Array for 100-GbE 40-km Reach Application

A monolithically integrated 100-Gb/s throughput (4 $,times,$25 Gb/s) laser array has been developed that employs frequency-modulated distributed Bragg reflector lasers. An optical filter converts a frequency-modulated signal to an amplitude-modulated signal with a high contrast ratio in addition to reducing the lasing spectrum bandwidth. A clear eye opening after 40-km transmission was observed with a 25-Gb/s nonreturn-to-zero signal in the 1550-nm region.      

High-power ultralow-chirp 10-Gb/s electroabsorption modulator integrated laser with ultrashort photocarrier lifetime

A high-power, ultralow-chirp electroabsorption modulator (EAM) integrated with a distributed-feedback laser diode (EML) having ultrashort lifetime of photogenerated holes in the EAM quantum-well (QW) structure is reported for the first time. A shallow QW structure having a small valence band offset to enhance the sweepout of photogenerated holes was employed as EAM absorption layer. The measured hole lifetimes were 7-11 ps, and the measured frequency chirp (/spl alpha/-parameter) was low or negative at low EAM reverse bias voltages even under high optical output power conditions. Successful 10-Gb/s 80-km normal-dispersion single-mode fiber transmission (chromatic dispersion D=1600 ps/nm) and the record average fiber optical output power (P/sub f/) of +5.3 dBm were achieved at 25/spl deg/C. In addition, semicooled operation of EML at enhanced bit rates has been demonstrated for application in small-form-factor protocol-agnostic optical transceivers. A 10.7-Gb/s 1600-ps/nm transmission was achieved at 45/spl deg/C and P/sub f/=+3.0 dBm.     

Optical Clock Recovery and 3R Regeneration for 10-Gb/s NRZ Signal to Achieve 10 000-hop Cascadability and 1 000 000-km Transmission

This letter experimentally demonstrates all-optical clock recovery and optical 3R regeneration for a 10-Gb/s nonreturn-to-zero (NRZ) format. The 3R regenerator has achieved 10 000-hop cascadability and 1 000 000-km transmission for a pseudorandom bit sequence (PRBS) of$2 ^7 -1$. A semiconductor-optical-amplifier-based Mach–Zehnder interferometer (SOA-MZI) as an NRZ to pseudoreturn-to-zero converter and a Fabry–PÉrot filter perform the all-optical clock recovery from an NRZ signal. A pair of SOA-MZIs combined with a synchronous modulator provides the 2R regeneration and retiming functions. The cascadablity of the 3R regenerator is investigated in a recirculating loop transmission experiment by eye diagram, bit-error rate, and$Q$-factor measurements. Transmission with the 3R regenerator shows significant performance improvement over that without 3R regeneration. A 100-hop cascadability is also demonstrated for PRBS$2 ^31 -1$, enabling 10 000-km error-free transmission with a low power penalty of 1.2 dB.     

A 1.7 Gb/s ASK and a 622 Mb/s incoherent FSK transmissionexperiment using a 1.55-μm multiquantum well distributed feedbacklaser

A multiple-quantum-well distributed-feedback (MQW-DFB) laser with narrow linewidth and low frequency chirp at low output power may experience linewidth rebroadening at high output power. the rebroadening is mostly due to a large carrier-induced change of refractive index, which also causes a large frequency modulation response for the MQW-DFB lasers. Using a 1.55-μm MQW-DFB laser, a 622-Mb/s amplitude-shift-keying (ASK) transmission experiment employing 200-km of fiber and an erbium-doped fiber amplifier has been demonstrated having a dispersion power penalty less than 9.8 dB. The receiver sensitivities at BER=10^-9 of the ASK system are -34.5 dBm and -42.5 dBm for 1.7-Gb/s and 622-Mb/s modulation, respectively. A 622-Mb/s incoherent frequency-shift-keying (FSK) transmission experiment using the same laser has also achieved a receiver sensitivity of -42.5 dBm     

EAM-integrated DFB laser modules with more than 40-GHz bandwidth

Electroabsorption modulator (EAM)-distributed feedback (DFB) modules with record-high bandwidth of 41 GHz have been developed. 40-Gb/s nonreturn to zero (NRZ) operation with 12-dB extinction ratio and -1.6-dBm average output power have been successfully achieved by optimizing the EAM length and detuning. A clearly opened eye diagram was maintained even after 80-km nonzero dispersion shifted fiber (NZ-DSF) transmission with dispersion compensation, 40-GHz short pulse trains with 6-ps pulsewidth have been also generated by sinusoidal electrical modulation     

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.     

Requirements for modulator-integrated DFB LD's for penalty-free2.5-Gb/s transmission

Wavelength chirp of modulator-integrated distributed-feedback laser diodes (DFB LD's) is governed by device parameters such as the modulator facet reflectivity, isolation resistance, grating coupling factor, and differential gain. We determined values of these parameters necessary for ensuring penalty-free 2.5-Gb/s transmission over at least 80-km of standard fiber. The influences of the device parameters on wavelength chirp behavior and 2.5-Gb/s data transmission performance are investigated using a new method of characterizing wavelength chirp. By transmitting light from the LD while modulating the modulator, we can determine the light intensity fluctuation after the transmission caused by wavelength chirp. This intensity fluctuation ratio (ΔI/I) is used to monitor the wavelength chirp. We use integrated devices which satisfy all these requirements, and which are grown by selective metal-organic vapor phase epitaxy (MOVPE), to demonstrate penalty-free 2.5-Gb/s transmission, even over 120-km of standard fiber     

Fully electrical 40-Gb/s TDM system prototype based on InP HEMTdigital IC technologies

This paper presents a fully electrical 40-Gb/s time-division-multiplexing (TDM) system prototype transmitter and receiver. The input and output interface of the prototype are four-channel 10-Gb/s signals. The prototype can be mounted on a 300-mm-height rack and offers stable 40-Gb/s operation with a single power supply voltage. InP high-electron mobility transistor (HEMT) digital IC's perform 40-Gb/s multiplexing/demultiplexing and regeneration. In the receiver prototype, unitraveling-carrier photodiode (UTC-PD) generates 1 V_pp output and directly drives the InP HEMT decision circuit (DEC) without any need for an electronic amplifier. A clock recovery circuit recovers a 40-GHz clock with jitter of 220 fs_pp from a 40-Gb/s nonreturn-to-zero (NRZ) optical input. The tolerable dispersion range of the prototype within a 1-dB penalty from the receiver sensitivity at zero-dispersion is as wide as 95 ps/nm, and the clock phase margin is wider than 70° over almost all the tolerable dispersion range. A 100-km-long transmission experiment was performed using the prototype. A high receiver sensitivity [-25.1 dBm for NRZ (2⁷-1) pseudorandom binary sequence (PRBS)] was obtained after the transmission. The 40-Gb/s regeneration of the InP DEC suppressed the deviation in sensitivity among output channels to only 0.3 dB. In addition, four-channel 40-Gb/s wavelength-division-multiplexing (WDM) transmission was successfully performed     

Output polarization control of fiber DFB laser using injectionlocking

Experimental results of a distributed feedback fiber laser injection locked to a Fabry-Perot laser diode are presented. By adjusting the injection power of the fiber laser to the Fabry-Perot laser, high quality laser output with a degree of polarization larger than 95% and sidemode suppression ratio higher than 45 dB was achieved. A 3.8-dB power penalty improvement was also demonstrated in a 41-km 10-Gb/s transmission experiment     

A 10 Gb/s high sensitivity, monolithically integrated p-i-n-HEMToptical receiver

A high-sensitivity, monolithically integrated optical receiver, composed of a p-i-n-PD and high electron mobility transistors (p-i-n-HEMTs) is described. The receiver sensitivity is -17.3 dBm at a bit error rate of 1×10^-9 for a 10-Gb/s non-return-to-zero (NRZ) lightwave signal. This value is the best result yet reported for 10-Gb/s monolithically integrated receivers. The sensitivity is -30.6 dBm if an erbium-doped fiber amplifier (EDFA) is placed ahead of the p-i-n-NEMT receiver. A transmission experiment using a 150-km dispersion-shifted fiber (DSF) indicates no degradation in the bit error rate characteristics or the eye pattern. This verifies the practicality of the p-i-n-HEMT optical receiver for high-speed transmission systems     

Frequency response of a unidirectional-output optical frequencyconversion device with an asymmetrical-κ DBR laser structure

The frequency response of a unidirectional-output optical frequency conversion device is measured. The device has a saturable absorber region within the active region, which acts as an optical gate for converted light. The 3-dB bandwidth of the device with saturable absorber region is measured up to 800 MHz, and is found to be limited by the frequency response of the saturable absorber region. To operate the device faster, lasing mode intensity modulation by input light is attempted by using the device in a laser diode mode. In this case, the electrodes of the saturable absorber and the gain regions are connected electrically, and the saturable absorber region is also biased far above the threshold condition at the same time with the gain region. The 3-dB bandwidth of the device increases to over 10 GHz, and the 10-Gb/s nonreturn-to-zero (NRZ) eye pattern can be observed when the input TM-polarized light intensity is modulated by a 10-Gb/s NRZ pseudorandom signal     

12.5-gb/s direct Modulation up to 115/spl deg/C in 1.3-/spl mu/m InGaAlAs-MQW RWG DFB lasers with notch-free grating structure

Direct modulation at 12.5 Gb/s of 1.3-/spl mu/m InGaAlAs distributed feedback (DFB) ridge waveguide (RWG) lasers with low-resistance notch-free gratings running up to 115/spl deg/C is experimentally demonstrated. It was achieved by the combination of the high differential gain of an InGaAlAs MQW active layer, high characteristic temperature of RWG structure, and low-resistance notch-free grating. Moreover, successful transmission of 10-Gb/s modulated signals over 30-km standard single-mode fiber was achieved with the laser running at up to 115/spl deg/C. These results confirm the suitability of this type of laser for use as the cost-effective light source in 12.5-Gb/s and 10-Gb/s datacom applications.     

1.3-μ m InGaAlAs Short-Cavity DBR Lasers for Uncooled 10-Gb/s Operation With Low Drive Current

We present a novel 1.3-mum laser, a short-cavity distributed-Bragg-reflector (DBR) laser that enables uncooled, 10-Gb/s operation with low drive currents. The laser consists of a short InGaAlAs multiple-quantum-well active region butt-jointed to an InGaAsP-DBR region. A fabricated laser with a 75-mum active region demonstrated 100 degC, 10-Gb/s operation at a record low drive current of 14-mA peak-to-peak (mA_p-p) with an average output power of -3 dBm     

NRZ operation at 40 Gb/s of a compact module containing an MQW electroabsorption modulator integrated with a DFB laser

NRZ operation at 40 Gb/s has been successfully performed using a very compact module of a multiple-quantum-well (MQW) electroabsorption modulator integrated with a distributed-feedback (DFB) laser. While the DFB laser is injected with a constant current, the integrated MQW electroabsorption modulator is driven with a 10-Gb/s electrical NRZ signal. A clearly opened eye diagram has been observed in the modulated light from the modulator. And a receiver sensitivity of -27.2 dBm at 10/sup -9/ has been experimentally confirmed in the bit-error-rate (BER) performance.     

1.25-Gb/s Operation of a Spectrum-Sliced Fabry–PÉrot Laser Diode With Intensity Noise Suppression by a Second Fabry–PÉrot Laser Diode

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.     

Transparent ultra-long-haul DWDM networks with "broadcast-and-select" OADM/OXC architecture

We describe an experimental realization of ultra-long-haul (ULH) networks with dynamically reconfigurable transparent optical add-drop multiplexers (OADMs) and optical cross-connects (OXCs). A simple new approach to dispersion management in ULH dense-wavelength-division-multiplexing (DWDM) transparent optical networks is proposed and implemented, which enables excellent transmission performance while avoiding dispersion compensation on a connection-by-connection basis. We demonstrate "broadcast-and-select" node architectures that take full advantage of this method. Our implementation of signal leveling ensures minimum variations of path-averaged power among the wavelength-division-multiplexing (WDM) channels between the dynamic gain-equalizing nodes and results in uniform nonlinear and spontaneous-emission penalties across the WDM spectrum. We achieve 80/spl times/10.7-Gb/s DWDM networking over 4160 km (52 spans/spl times/80 km each) of all-Raman-amplified symmetric dispersion-managed fiber and 13 concatenated OADMs or 320/spl times/320 wavelength-port OXCs with 320-km node spacing. The WDM channels use 50-GHz grid in C band and the simple nonreturn-to-zero (NRZ) modulation format. The measured Q values exhibit more than a 1.8-dB margin over the forward-error correction threshold for 10/sup -15/ bit-error-rate operation. We compare these results with point-to-point transmission of 80/spl times/10-Gb/s NRZ WDM signals over 4160 km without OADM/OXC and provide detailed characterization of penalties due to optical signal-to-noise-ratio degradation, filter concatenation, and crosstalk.     

基于反射半导体光放大器与光纤布拉格光栅均衡器的单波长10Gb/s WDM PON光传输方案（英文）

We propose a 10-Gb/s WavelengthDivision-Multiplexed Passive Optical Network(WDM-PON) scheme with upstream transmission employing Reflective Semiconductor Optical Amplifier(RSOA) and Fibre Bragg Grating(FBG) optical equaliser.Transmissions of10-Gb/s non return-to-zero signals using a 1.2-GHz RSOA and FBG optical equaliser with different setups are demonstrated.Significant performance improvement and 40-km standard single mode fibre transmission are achieved using FBG optical equaliser and Remotely Pumped Erbium-Doped Fibre Amplifier(RP-EDFA),where they are used to equalise the output of the band-limited RSOA and amplify the seed light and upstream signal,respectively.     

High-Performance and Low-Cost 40-Gb/s CWDM Optical Modules

High-performance and low-cost 40-Gb/s optical modules using four different wavelength uncooled 10-Gb/s distributed-feedback (DFB) lasers are proposed and demonstrated. The 40-Gb/s optical module was integrated with coarse wavelength division multiplexing (CWDM) thin-film filters which enabled four 10-Gb/s transmission channels output through a single fiber. The 10-Gb/s DFB laser was packaged by commercialized low-cost coaxial TO-Can technology. The results of the 40-Gb/s optical module showed that the output optical power was above ${-}1$ dBm per channel and the system power budget was 12 dB. The transmission distance with a single-mode fiber reached more than 30 km at a bit-error-rate of $10^{{-}9}$. Compared with conventional 40-Gb/s optical modules, the module is easy to fabricate and is low cost. This proposed high-performance 40-Gb/s CWDM optical module demonstrates not only the feasibility of a 30 km transmission, but also shows the low-cost possibility of ensuring the application of WDM-passive optical network fiber-to-the-home systems.      

Multiple input detection and digital signal processing for uncooled ONUs in a TWDM-PON with a commercial WDM demultiplexer

A simple uplink transmission scheme with multiple-input direct detection and digital signal processing has been proposed and experimentally demonstrated for the time and wavelength division multiplexed passive optical networks (TWDM-PONs), to allow wavelength drift of lasers at the uncooled optical network units (ONUs). In our experiment, after passing by the commercial 100-GHz WDM demultiplexer, three 10-Gb/s NRZ signals with minimum signal wavelength separation of 50-GHz can be recovered successfully after 50-km standard single-mode fiber (SSMF) transmission. Simulation results are also obtained to analysis the receiver sensitivity at different wavelength separations and discuss methods improving power budget.