10-Gb/s, 80-km SMF Transmission From 0 to 80 $^{circ}$C by Using L-Band InGaAlAs-MQW Electroabsorption Modulated Laser With Twin Waveguide Structure

A 10-Gbit/s, 1.58-mu m, InGaAlAs electroabsorption modulator (EAM) integrated distributed-feedback (DFB) laser (EML) with a twin waveguide (TWG) structure is operated experimentally over a wide temperature range of 0 to 80degC. We introduce an InGaAlAs multi-quantum well (MQW) system for both LD and EAM MQWs, because this material has temperature-tolerant characteristics. These layers are grown using single step epitaxial growth, and the device was fabricated with a very simple process. Moreover, successful transmission through an 80-km single-mode fiber (SMF) was achieved with the device running at up to 80degC. These results confirm the suitability of this type of laser for use as a cost-effective and low-power consumption light source in 10-Gbit/s optical network systems.     

40-Gb/s Direct Modulation With High Extinction Ratio Operation of 1.3-μm InGaAlAs Multiquantum Well Ridge Waveguide Distributed Feedback Lasers

Direct modulation at 40 Gb/s of a 1.3-mum InGaAlAs distributed feedback ridge waveguide laser is experimentally demonstrated. By combination of the high differential gain of an InGaAlAs multiquantum well active layer, a short cavity length of 100 mum, and a low-resistance notch-free grating, it achieves high bandwidth of 29 GHz and high-extinction ratio of 5 dB at 40-Gb/s modulation. Moreover, the laser operates at a record maximum ambient temperature of 60degC under 40-Gb/s directly modulation. It also achieves 40-Gb/s modulated transmission over 2 km with a low power penalty of 0.25 dB at 25degC .     

Highly Reliable 1.5-μm DFB Laser With High-Mesa SIBH Structure

The degradation behavior of 1.5-mum uncooled distributed feedback (DFB) lasers with a semi-insulating buried heterostructure during constant-power aging is investigated. Long-term stability is achieved by suppressing the t^0.5 deterioration in the current increase rate (second-stage degradation). The improvement in reliability is attributed to the fact that some defects on the grating interface are simultaneously suppressed by the mutual diffusion that occurs when growing the SI-InP layer. We realized a DFB laser with high reliability (< 1000 failure digits) at 95 degC that is capable of error-free 2.5-Gb/s 80-km transmission at -20degC to 100 degC     

30-gb/s signal transmission over 40-km directly modulated DFB-laser-based single-mode-fiber links without optical amplification and dispersion compensation

Based on a recently proposed novel optical-signal-modulation technique of adaptively modulated optical orthogonal frequency-division multiplexing (AMOOFDM), numerical simulations of the transmission performance of AMOOFDM signals are undertaken in directly modulated DFB laser (DML)-based single-mode-fiber (SMF) links without optical amplification and dispersion compensation. It is shown that a 30-Gb/s transmission over a 40-km SMF with a loss margin of greater than 4.5 dB is feasible in the aforementioned simple configuration using intensity modulation and direct detection (IMDD). In addition, the DFB-laser frequency chirp and the transmission-link loss are identified to be the key factors limiting the maximum achievable transmission performance of the technique. The first factor is dominant for transmission distances of < 80 km and the second one for transmission distances of > 80 km. It is also observed that fibers of different types demonstrate similar transmission performances, on which fiber nonlinear effects are negligible.     

10-Gb/s Direct Modulation up to 100 $^{circ}$C Using 1.3- $mu$m-Range Metamorphically Grown Strain Compensated InGaAs–GaAs MQW Laser on GaAs Substrate

We have realized 10-Gb/s direct modulation up to 100degC using a metamorphic InGaAs multiple-qunatum well (MQW) laser on a GaAs substrate. The highly strained InGaAs quantum well (QW) and strain-compensated GaAs barrier layer allowed 1.3-mum-range lasing and an increased number of QWs (six). This laser with a 200-mum-long short cavity and a narrow ridge had maximum relaxation oscillation frequencies of 13 and 6 GHz at 25degC and 100degC, respectively. A 10-km single-mode fiber error-free transmission was successfully obtained at a temperature of 85degC .     

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     

Extended Transmission Reach Using Optical Filtering of Frequency-Modulated Widely Tunable SSG-DBR Laser

We propose a novel transmitter consisting of a frequency-modulated widely tunable super-structure-grating distributed Bragg reflector (SSG-DBR) laser and an optical filter. The SSG-DBR laser acts as a frequency modulating light source with a constant output power by modulating the reverse bias voltage in the phase control (PC) region. By optically filtering the output light from the frequency-modulated laser, we have demonstrated 60- and 180-km transmissions for 20- and 10-Gb/s nonreturn-to-zero (NRZ) signals, respectively. The power penalty was 2.2 dB after the 180-km transmission of a 10-Gb/s NRZ signal as determined by bit-error-rate measurements. Furthermore, an extended transmission reach was achieved with a wide tuning range without controlling the bias and modulating voltages in the PC region.     

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.      

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     

The first hot pluggable 2.5 Gb/s DWDM transceiver in an SFP form factor

For the first time, a hot pluggable 2.5 Gb/s DWDM transceiver with 100 GHz spacing in an SFP form factor has been presented. We demonstrate transmit wavelength drift of plusmn9 pm and optical output power stability of 0.2 dB over an operating case temperature range of -5degC to 70 degC. The minimum receive sensitivity was -33.2 dBm for back-to-back, -32.6 dBm after transmission over 80 km of standard SMF, and -28 dBm for an OSNR level of 16 dB at a BER of 1 times 10^-10      

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.     

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.     

Low insertion loss and low dispersion penalty InGaAsP quantum-well high-speed electroabsorption modulator for 40-Gb/s very-short-reach, long-reach, and long-haul applications

We present a metal-organic-chemical-vapor-deposition-grown low-optical-insertion-loss InGaAsP/InP multiple-quantum-well electroabsorption modulator (EAM), suitable for both nonreturn-to-zero (NRZ) and return-to-zero (RZ) applications. The EAM exhibits a dynamic (RF) extinction ratio of 11.5 dB at 1550 nm for 3 Vp-p drive under 40-Gb/s modulation. The optical insertion loss of the modulator in the on-state is -5.2 dB at 1550 nm. In addition, the EAM also exhibits a 3-dB small-signal response (S21) of greater than 38 GHz, allowing it to be used in both 40-Gb/s NRZ and 10-Gb/s RZ applications. The dispersion penalty at 40 Gb/s is measured to be 1.2 dB over /spl plusmn/40 ps/nm of chromatic dispersion. Finally, we demonstrate 40-Gb/s transmission performance over 85 km and 700 km.     

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     

A Large Swing, 40-Gb/s SiGe BiCMOS Driver With Adjustable Pre-Emphasis for Data Transmission Over 75 $Omega$ Coaxial Cable

A fully differential 40-Gb/s cable driver with adjustable pre-emphasis is presented. The circuit is fabricated in a production 0.18 mum SiGe BiCMOS technology. A distributed limiting architecture is used for the driver employing high-speed HBTs in the lower voltage predriver, and a high-breakdown MOS-HV-HBT cascode, consisting of a 0.18 mum n-channel MOSFET and a high-voltage HBT (HV-HBT), for the high voltage output stages. The circuit delivers up to 3.6 V peak-to-peak per side into a 75 Omega load with variable pre-emphasis ranging from 0 to 400%. S-parameter measurements show 42 dB differential small-signal gain, a 3-dB bandwidth of 22 GHz, gain peaking control up to 25 dB at 20 GHz and input and output reflection coefficients better than -10 dB up to 40 GHz. Additional features of the driver include output amplitude control (from 1 V_pp to 3.6 V_pp per side), pulse-width control (35% to 65%) and an adjustable input dc level (1.1 V to 1.8 V) allowing the circuit to interface with a SiGe BiCMOS or MOS-CML SERDES. The transmitter is able to generate an eye opening at 38 Gb/s after 10 m of Belden 1694 A coaxial cable which introduces 22 dB of loss at 19 GHz. Measurement results also demonstrate that the transmitter IC operates as a standalone equalizer for 10-Gb/s data transmission over 40 m of Belden cable without the need for receiver equalization.     

Uncooled 25 Gbit/s direct modulation of semi-insulating buried-heterostructure 1.3 μm AlGaInAs quantum-well DFB lasers

Uncooled 25 Gbit/s direct modulation of 1.3 mum DFB lasers is demonstrated. The 150 mum-long semi-insulating buried-heterostructure AIGalnAs quantum-well DFB lasers show clear eye-openings with dynamic extinction ratio of 5 dB up to 70degC. 13 km singlemode-fibre transmission experiments using the devices show low power penalty within 1.3 dB between 25 and 70degC. These characteristics are the first achievement by 1.3 mum directly modulated lasers.     

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.      

40 Gbit/s electroabsorption modulated distributed feedback laser

A 40 Gbit/s multi-quantum well (MQW) electroabsorption modulator (EAM) with a lumped electrode monolithically integrated with a distributed feedback (DFB) laser is demonstrated. Superior characteristics are exhibited for the device, such as low threshold current of 18 mA, over 40 dB side-mode suppression ratio at 1 550 nm and more than 30 dB extinction ratio when coupled into a single-mode fiber. By adopting deep ridge waveguide and planar electrode structures combined with buried benzocyclobutene (BCB), the capacitance of the EAM is reduced down to 0.18 pF and over 33 GHz modulation bandwidth at a small signal has been demonstrated. Negative chirp operation is realized when the bias voltage is beyond 1.6 V.     

Theoretical investigation of 8 /spl times/ 10-Gb/s WDM signal transmission performance based on gain-equalized SOAs using backward Raman pumping at DCF

We have theoretically investigated 8 /spl times/ 10-Gb/s wavelength-division multiplexing (WDM) signal transmission characteristics based on semiconductor optical amplifiers (SOAs) with equalized gain using discrete Raman amplification (DRA). Gain equalization and low noise figures have been obtained by adjusting the backward Raman pumping power and wavelength at a dispersion compensating fiber (DCF) for each span. Bit-error-rate characteristics were calculated for 8 /spl times/ 10-Gb/s WDM signal transmission over 6 /spl times/ 40-km single-mode fiber (SMF) + DCF links with gain-equalized SOAs using DRAs at DCF. Approximately a 2.5-dB improvement of the receiver sensitivity was achieved by using SOAs and DRAs with optimized Raman pumping. One can easily upgrade the transmission length of a link based on SOAs with an appropriate backward pump laser at each DCF.     

40-Gb/s WDM transmission with virtually imaged phased array (VIPA) variable dispersion compensators

We have demonstrated variable dispersion compensation by using a virtually imaged phased array (VIPA) to overcome the small dispersion tolerance in 40-Gb/s dense wavelength-division multiplexing (WDM) transmission systems. By utilizing the periodical characteristics of VIPA compensators, we performed simultaneous dispersion compensation in a 1.28-Tb/s (40-Gb/s/spl times/32 ch; C band) short-haul transmission and confirmed that only two VIPA compensators and one fixed dispersion-compensating fiber are required for a large transmission range of 80 km. This performance can greatly reduce the cost, size, and number of compensator menus in a 40-Gb/s WDM short-haul transmission system. In addition, we achieved 3.5-Tb/s (43-Gb/s/spl times/88 ch; C and L bands) transmission over a 600-km nonzero dispersion-shifted fiber by using VIPA compensators. Although channel-by-channel dispersion compensation is required due to the larger residual dispersion slope in long-haul transmission, the periodical characteristics of the VIPA compensators offer the advantage of considerably reducing the number of different modules required to cover the whole C (or L) band. An adequate optical signal-to-noise ratio, which was the same for all channels, was-obtained by using distributed Raman amplification, a gain equalizer, and a preemphasis technique. We achieved a Q-factor of more than 11.8 dB; (BER<10/sup -17/ with forward-error correction) for all 88 channels.