Low Power Penalty Research Articles

Low power penalty 80 to 10 Gbit/s OTDM demultiplexer using standing-wave enhanced electroabsorption modulator with reduced driving voltage

Low power penalty 80 to 10 Gbit/s demultiplexing using a novel standing-wave enhanced electroabsorption modulator is reported. In this new design, an electrical standing-wave pattern is formed deliberately along the travelling-wave electrodes, reducing the driving voltage required for high-speed demultiplexing.

Low-chirp and external optical feedback resistant characteristics in λ/8 phase-shifted distributed-feedback laser diodes under direct modulation

Clarifies that phase shift value in directly modulated distributed feedback laser diodes (DFB-LDs) affects their chirp characteristics and resistance to external optical feedback because of the feedback effect of mirror loss (FEML). Comparing /spl lambda//8, /spl lambda//4, and 3//spl lambda/8 phase-shifted DFB-LDs, theoretically and experimentally, showed that the negative FEML in /spl lambda//8 phase-shifted DFB-LDs improves their transmission performance and makes them more resistant to external optical feedback. It was demonstrated with 2.5-Gb/s directly modulated 1.55-/spl mu/m /spl lambda//8 phase-shifted DFB-LDs that a very low-power penalty for 100-km transmissions (less than 1 dB for BER=10/sup -10/) can be obtained within a wide extinction ratio from 8.5 to 14.5 dB. Excellent resistance to optical feedback was also demonstrated using /spl lambda//8 phase-shifted DFB-LDs: isolator-free 80-km transmission was successful under -14-dB external optical feedback. In addition, the relation of transmission characteristics to coupling coefficient /spl kappa/L and detuning between oscillation wavelength and gain maximum was also discussed here for designing low chirp /spl lambda//8 phase-shifted DFB-LDs.

Filter-free all-optical wavelength conversion using Sagnac interferometer integrated with parallel-amplifier structure (SIPAS)

A Sagnac interferometer integrated with a parallel-amplifier structure (SIPAS) is proposed for filter-free all-optical wavelength conversion. A Mach-Zehnder interferometer with a semiconductor optical amplifier in each arm is monolithically integrated with a Sagnac interferometer. Clear eye opening and low power penalty of 0.9 dB were achieved at a bit rate of 10 Gbit/s using the fabricated SIPAS.

Isolator-free 2.5-Gb/s 80-km transmission by directly modulated /spl lambda//8 phase-shifted DFB-LDs under negative feedback effect of mirror loss

It was verified for the first time that phase-shift value in directly modulated DFB laser diodes (LDs) affects their chirping characteristics and external optical feedback resistance due to the feedback effect of mirror loss (FEML). Theoretical and experimental results clarified that the negative FEML achieved in /spl lambda//8 phase-shifted DFB-LDs was able to improve the transmission performances and make the LDs more robust to external optical feedback. Isolator-free 80-km transmissions with a very low power penalty of less than 1-dB at bit error rate (BER)=10/sup -10/ was demonstrated with 2.5-Gb/s directly modulated 1.55-/spl mu/m /spl lambda//8 phase-shifted DFB-LDs.

High-speed (11 Gbit/s) data transmission using perfluorinated graded-index polymer optical fibers for short interconnects (<100 m)

Perfluorinated graded-index polymer optical fibers (GI-POF's) have been developed that offer low losses (<50 dB/km) and high bandwidth (>0.3 GHz km) at data communication wavelengths (0.85 and 1.3 μm). Here we demonstrate that such fibers can support data rates up to 11 Gbit/s for 100 m with low-power penalty and large-power margins. Although a restricted launch was used, differential mode delay measurements show that, in a large central region of the fiber core (50% of the core diameter), very large bandwidths can be obtained with modest alignment requirements. These improved transmission characteristics (obtained using inexpensive, uncooled, unisolated 1.3-μm Fabry-Perot sources and pin detectors) together with potential low-cost connectorization and a small fiber bend-radius make perfluorinated GI-POF's a candidate for premise networks and short-reach telecom and computer interconnections.

Limiting-amplified multiwavelength dispersion compensator incorporating chirped fiber gratings and optical amplifier for DWDM systems

An optical limiting-amplified multiwavelength dispersion compensator (LDC), incorporating multiple chirped fiber gratings and a common bidirectional erbium-doped fiber amplifier, for dense wavelength-division-multiplexing (DWDM) systems is proposed and demonstrated. The LDC provides simultaneous dispersion compensation and limiting amplification of multiple DWDM signals. A high constant channel output power of 16.4 dBm and a low power penalty of less than 0.3 dB over an input signal dynamic range of −17 to 0 dBm can be obtained for this LDC in a 10 Gb/s two-wavelength 80-km conventional single-mode fiber system. The LDC may facilitate easier DWDM system design flexibility and network implementation.

100 Gbit/s wavelength conversion using FWM in anMQW semiconductor optical amplifier

Wavelength conversion of a 100 Gbit/s optical time division multiplexing signal has been achieved using four wave mixing in a 2 mm multiquantum well semiconductor optical amplifier and a Bragg fibre grating for filtering. Error free operation of all 10 channels was achieved with low power penalties.

1.3-μm InP-based quantum-well lasers with n-doped separate confinement heterostructure layers for high-temperature operation

We present a novel approach for reducing the light output power penalty in 1.3-μm InP-based strained-layer (SL) MQW lasers at elevated temperatures. It is shown that n-type doping in the separate confinement heterostructure (SCH) layers increases the barrier height in the valence band profiles effectively, which makes it possible to suppress the pile-up of holes in the SCH region under high-temperature, high-injection conditions. One significant impact of this approach is that the power penalty can be reduced to one half of that in conventional SL-MQW lasers with undoped SCH. We show that SL-MQW structures with n-doped SCH have a great potential for realizing a low power penalty as well as high efficiency in InP-based MQW lasers at elevated temperatures.

Experimental demonstration of a multiple-/spl lambda/ wavelength shifter for dynamically reconfigurable WDM networks

We demonstrate a multiple-/spl lambda/ wavelength shifter that is based on temporal interleaving and semiconductor optical amplifier cross-gain compression. Our multiple-/spl lambda/ wavelength shifter is transparent to both the nonreturn-to-zero (NRZ) and return-to-zero (RZ) input data-formats. We simultaneously wavelength shift two independent NRZ 1-Gb/s WDM channels from 1548 and 1552 nm to 1540 and 1569 nm, respectively, with low-power penalties.

Repeated wavelength conversion of 10 Gb/s signals and converted signal gating using wavelength-tunable semiconductor lasers

Repeated wavelength conversion of 10 Gb/s pseudorandom nonreturn-to-zero signals is demonstrated using semiconductor lasers that can be tuned wavelength over a broad range. Error-free tunable wavelength conversion with a very low power penalty can be achieved in both first and second wavelength conversion over a broad wavelength range from 1.486-1.573 /spl mu/m. The converted signal can be switched rapidly within this wavelength region. High-speed converted signal gating controlled by adjusting the bias current to the device active region is also demonstrated.

All-optical data format conversions and reconversions between the wavelength and time domains for dynamically reconfigurable WDM networks

We demonstrate all-optical error-free 2 Gb/s data format conversions and reconversions between the wavelength and time domains. Conversion between these two domains is accomplished by performing single-stage TDM-to-WDM and WDM-to-TDM conversions. We also perform the function of converting back all-optically to the original domain by performing both WDM-to-TDM-to-WDM and TDM-to-WDM-to-TDM reconversions. All conversions and reconversions are realized by using the cross gain compression mechanism inherent in semiconductor optical amplifiers (SOA's). We first demonstrate our TDM-to-WDM converter by simultaneously time demultiplexing and wavelength shifting a four-channel 2 Gb/s TDM data stream into four 500 Mb/s WDM channels. Moreover, we extend this single-stage approach by demonstrating a two-stage TDM-to-WDM converter consisting of two cascaded single-stage TDM-to-WDM modules. This two-stage converter selectively time demultiplexes and wavelength shifts a four-channel 2 Gb/s TDM data stream into two 500 Mb/s WDM channels after the second stage. Furthermore, we demonstrate a WDM-to-TDM converter by simultaneously time multiplexing and wavelength shifting the data from two 1 Gb/s WDM channels into one 2 Gb/s TDM signal. Finally, we demonstrate reconversion between the wavelength and time domains for two channels by performing both WDM-to-TDM-to-WDM and then TDM-to-WDM-to-TDM reconversions. In order to demonstrate system robustness, we use 80 km of fiber and three EDFA's between the conversion and reconversion stages. We show that reconverting back to the TDM data format requires an interstage WDM channel wavelength range less than /spl sim/4 nm, due to the power penalty induced by the interstage relative phase shift between the channels. This constraint limits the operation of the TDM-to-WDM-to-TDM reconverter to data rates up to 10 Gb/s and interstage distances to /spl sim/100 km. All demonstrated conversion and reconversion processes are accomplished with low power penalties. These conversion and reconversion schemes could be useful in WDM switching nodes and may serve as key building blocks for all-optical WDM networks.

Experimental demonstrations of all-optical conversions between the RZ and NRZ data formats incorporating noninverting wavelength shifting leading to format transparency

We demonstrate a unique semiconductor optical amplifier based system that performs the converting functions of: 1) RZ-to-NRZ; and 2) NRZ-to-RZ-to-NRZ by using noninverting cross-gain compression wavelength shifting. Our robust NRZ-to-RZ-to-NRZ reconverter was tested using 80 km of fiber and 4 EDFA's. We show that at 1-Gb/s, both functions can be realized with low power penalties (<2.0 dB).

The dependence of carrier lifetime on spectral width in multimode semiconductor lasers

Comprehensive measurements of the dependence of the carrier lifetime, eye pattern, and power penalty on the spectral width in multimode semiconductor lasers for a gigabit lightwave transmission system are presented. The results show that the carrier lifetime, eye pattern, and power penalty caused by mode partition noise (MPN) are strongly dependent on the source spectral width. The lasers with shorter carrier lifetimes exhibit a narrow spectral width, and hence show less MPN, a better eye opening, and a lower power penalty. A theoretical calculation of the MPN-induced power penalty is in good agreement with the measured system penalties. The likely cause for narrow spectral width with shorter carrier lifetime of the lasers is due to the smaller linewidth enhancement factor a caused by a higher doping concentration in the lasers.

All-optical TDM-to-WDM data format conversion in a dynamically reconfigurable WDM network

We demonstrate both single-stage and two-stage all-optical TDM-to-WDM data format convertors based on cross-gain compression in an SOA. Our method simultaneously time demultiplexes and wavelength shifts each channel's data within a TDM packet. We convert a 2-Gb/s 4-channel TDM data stream at 1552 mn into four 500-Mb/s WDM channels at 1535, 1537, 1540, and 1571 mm. Moreover, we extend this single-stage approach by demonstrating a two-stage TDM-to-WDM convertor that selectively time demultiplexes and wavelength shifts a 2-Gb/s TDM input data stream into two 500-Mb/s WDM channels after the second stage. We find that low power penalties (<2 dB) can be achieved by using this scheme for both the single- and two-stage cases. This conversion scheme may be quite useful in WDM switching nodes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

100 Gbit/s, 500 km optical transmission experiment

Nearly penalty free 100 Gbit/s, 500 km optical transmission is successfully demonstrated using transform-limited optical pulses. By optimising the signal wavelength, low power penalties of 0.2 and 1.6 dB are achieved after 200 and 500 km, respectively.

Effect of carrier lifetime on mode partition noise in multimode semiconductor lasers

The dependence of mode partition noise (MPN), and its association with the eye diagram and power penalty, on carrier lifetime in 1.3 μm InGaAsP multimode semiconductor lasers for a 1.2 Gbit/s lightwave transmission system was investigated. It was found that lasers with shorter carrier lifetimes showed less MPN, and hence, a better eye opening and a lower power penalty, than the lasers with longer carrier lifetimes. The significant dependence of MPN, eye opening, and power penalty on carrier lifetime in multimode semiconductor lasers suggests that the carrier lifetime of the laser, which depends on the laser design, can be used as an important parameter for characterizing the performance of high-speed lightwave transmission systems.

Extremely low power penalty in 2.5‐Gb/S transmission experiment using 1.55‐μm MQW‐DFB lasers with optimized QW number

AbstractFor 1.55‐μm MQW‐DFB lasers, the dependence of transmission characteristics under 2.5‐Gb/s modulation on the number of wells is investigated experimentally and theoretically. The fiber length is 70 km and the total dispersion is 1470 ps/nm. Extremely low power penalty of 1.3 dB is obtained for a 12‐well laser with large differential gain of 7.1 × 10−16 cm2. © 1994 John Wiley &amp; Sons, Inc.

2-D WDM optical interconnections using multiple-wavelength VCSEL's for simultaneous and reconfigurable communication among many planes

A novel interconnection configuration in which one two-dimensional plane can communicate simultaneously and reconfigurably with many planes by using wavelength-division-multiplexing (WDM) is proposed and analyzed. This system incorporates arrays of multiple-wavelength vertical-cavity surface-emitting lasers (VCSELs) as well as wavelength-selective detecting planes. High signal contrast ratio with low power penalty can be achieved for a channel separation>30 nm, limited only by the detector spectral response. By using WDM pixels, the system capacity is significantly enhanced as compared to more traditional techniques. >

A study on an active square-law combining method for a polarization-diversity coherent optical receiver

A polarization-diversity coherent optical receiver which realizes ideal square-law combining with active gain control is described. This receiver can suppress the additional power penalty due to the demodulator dynamic range limitation by equivalently expanding the demodulator dynamic range. A low-power penalty less than 1 dB was attained with a 400-Mb/s FSK (frequency-shift keyed) single-filter detection system. Throughout a 25-h 183-km transmission experiment, the stable operation of this receiver was confirmed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>