H. Nakajima

A new distributed Bragg reflector laser for improved tuning

We propose a new distributed Bragg reflector laser using the phase variation of the Bragg facet reflectivity to improve the tunability. The modelling yields a 20 nm tuning range corresponding to a 8 nm increase of the classic DBR tunability. Preliminary experimental results confirmed this tuning improvement.<<ETX>>

Subnanosecond tunable laser using a single electroabsorption tuning super structure grating

A new tunable laser structure using a single electroabsorption (EA) tuning super structure grating section for fast wavelength switching operation, has been realized. The tuning mechanism of this absorption change distributed Bragg reflector (DBR) laser is based on a localized absorption variation induced in a multielectrode EA-SSG section. These devices exhibit a 2.5-nm tuning range with three modes and a switching time, between two successive wavelength channels, shorter than 250 ps. The output power variation under tuning is lower than 1.2 dB.

Full-duplex performance assessment of in-line transceivers emitting at 1.3 μm and receiving at 1.55 μm

Starting from the signal-to-noise ratio formula for in-line transceivers, we evaluate the receiver performance in full-duplex operation. We show theoretically and experimentally two methods to obtain a system compatible sensitivity. Full-duplex sensitivities of -23.9 dBm and -19.1 dBm are demonstrated at 68 Mb/s and 196 Mb/s, respectively.

Very low chirping of InGaAs-InGaAlAs MQW DFB BRS lasers under 10 Gbit/s modulation

The ability of the InGaAs/InGaAlAs multi-quantum-well (MQW) system to achieve ultra-low-chirp operation under 10-Gb/s operation is experimentally demonstrated. The MQW active layer has been grown by a solid-source molecular beam epitaxy (MBE) method. Two metalorganic chemical vapor deposition (MOCVD) regrowths were used to fabricate the distributed-feedback (DFB) buried ridge structure (BRS) lasers. DFB BRS lasers with good static and spectral performance have been obtained. Under 10-Gb/s modulation those lasers exhibited a chirp value as low as 0.11 nm at -20 dB, which is attributed to an extremely small phase-amplitude coupling coefficient of 1.8. An analysis of the AM and FM modulated laser field under digital pseudorandom signal confirms the observed spectra and shows the possibility of an optimum spectrum width for lasers with small chirping. >

A new tunable laser using a single electroabsorption tuning super structure grating for subnanosecond switching applications

A new tunable laser structure using a single electroabsorption (EA) tuning super structure grating (SSG) section for fast wavelength switching operation is reported. Instead of index change by carrier density or by thermal variation, the tuning mechanism of this absorption change (AC) distributed Bragg reflector (DBR) InGaAsP strained QW laser is based on a localized absorption variation induced in a Franz-Keldysh EA SSG section used as Bragg reflector. According to a simulation which takes into account the absorption and refractive index variations of the SSG section versus voltage and wavelength, an optimized device theoretically allows a wide tuning range of up to 11 nm with nine regularly spaced wavelength channels. Over this whole tuning range, the variation of the AC-DBR laser threshold gain is lower than 2 cm/sup -1/. Compared to a standard DBR laser exhibiting an 8-cm/sup -1/ threshold gain variation for the same wavelength shift, this AC-DBR laser would present extremely low threshold current and emitted power variations under tuning. Owing to its tuning mechanism, the switching time of the AC-DBR laser is independent of the wavelength shift, and only limited by the parasitic capacitance of the SSG ridge section. A test structure, easier to realize, with only a theoretical tuning range of 3 nm over four regularly spaced channels has been fabricated. These devices exhibiting a tuning range of 2.5 nm with three modes, present threshold current and output power variations under tuning of less than 8 mA and 1.2 dB, respectively. A switching time between two successive wavelength channels shorter than 250 ps has been observed, in agreement with typical capacitances of 0.8 pF/100 /spl mu/m measured on the SSG section.

Versatile in-line transceiver chip operating in two full-duplex modes at 1.3 and 1.55 μm

We describe a transceiver chip which can perform full-duplex operation alternatively in the 1.3 /spl mu/m (TX)/1.5 /spl mu/m (RX) or 1.5 /spl mu/m (TX)/1.3 /spl mu/m (RX) mode. A full duplex sensitivity of -28.4 dBm is reported for the transceiver mode emitting at 1.55 /spl mu/m and receiving at 1.3 /spl mu/m.

SOA-Based Label Extractor for Optical Burst Switching Application

This letter presents experimental results of a label extractor for labeled-optical burst switching (OBS) applications. The extractor uses a semiconductor optical amplifier in the amplifying detection mode to extract the label part of a burst with attached payload. More than 4-dB input power range is obtained with two burst sizes proving that the proposed solution is suitable for label detection in OBS nodes with asynchronous arrival of bursts. In addition, the solution brings an optical gain that is an interesting feature in such architectures.

Time-resolved spectrum characteristics of FSK-modulated dual-mode DFB/DBR lasers

A laser structure enabling simultaneous emission into distributed feedback (DFB) and distributed Bragg reflector (DBR) modes is characterized regarding frequency-shift keying (FSK)-modulated millimeter wave generation. Nonreturn-to-zero (NRZ)-modulation characteristics are measured by using time-resolved spectrum measurement techniques. A high FM efficiency of about 1.3 GHz/mA is reported at 622 Mb/s for 100-GHz-range millimeter waves.

High speed narrow linewidth 1.55 mu m GaInAs/AlGaInAs MQW DFB lasers

The authors report the successful realization of InGaAs/InGaAlAs MQW (multiquantum well) active layer DFB (distributed feedback) BRS (buried ridge structure) lasers with good static, dynamic, and spectral performances, together with a very low linewidth enhancement factor measured above threshold. They present an improved set of characteristics on 6-well InGaAs/InGaAlAs DFB BRS lasers, suitable for 10-Gb/s operation. An open eye diagram observed under 10-Gb/s strong signal modulation confirms the potential interest of the aluminium system for low chirp lasers modulated at high bit rates.<<ETX>>