Sampled-grating Distributed Bragg Reflector Laser Research Articles

Thermally Controlled Wavelength Locker Integrated in Widely Tunable SGDBR-LD Module

A sampled-grating distributed Bragg reflector laser module having an integrated multiwavelength locker has been developed and evaluated. The uniquely designed wavelength locker made of thermally controlled etalon has provided uniform wavelength monitoring and very stable wavelength locking in the 188-ITU grid channels (37 nm) with 25-GHz spacing. Over the case temperature from -5/spl deg/C to 65/spl deg/C, the laser wavelength was locked within /spl plusmn/0.5 GHz, and the total power consumption of the module was less than 4 W.

Single-Chip Wavelength Conversion Using a Photocurrent-Driven EAM Integrated With a Widely Tunable Sampled-Grating DBR Laser

Tunable photocurrent-driven wavelength converters using widely tunable sampled grating distributed Bragg reflector lasers, electroabsorption modulators, semiconductor optical amplifiers, and an optically preamplified receiver have been fabricated and tested. Dynamic wavelength conversion has been achieved over 40 nm with optical bandwidths up to 10 GHz.

Sampled-grating DBR laser integrated with SOA and tandem electroabsorption modulator for chirp-control

Chirp-controlled optical modulation is demonstrated using a voltage division scheme applied to a long-section phase modulator to compensate for the positive chirp of an electroabsorption modulator arranged in a tandem configuration. Both modulators are integrated with a semiconductor optical amplifier (SOA) and a sampled-grating distributed Bragg reflector (DBR) laser. The effective chirp factor can be controlled from +1 to -0.86 with less than 2 dB penalty in extinction ratio and insertion loss.

Design and Analysis of Widely Tunable Sampled Grating DFB Laser Diode Integrated With Sampled Grating Distributed Bragg Reflector

A new widely tunable laser diode structure that requires only two tuning currents is proposed. The laser diode consists of a sampled grating distributed feedback (SGDFB) laser diode monolithically integrated with a sampled grating distributed Bragg reflector (SGDBR). The phase control sections are properly inserted between the grating bursts of the SGDBR and SGDFB sections for the discrete and continuous tuning. To confirm the feasibility of the new structure, the split-step time domain model is used. The simulation result for a particular design shows that the tuning range as wide as 27 nm is possible with side-mode suppression ratio exceeding 35 dB. Furthermore, the output power is larger than that from SGDBR laser diodes with similar parameters.

Tunable Semiconductor Lasers: A Tutorial

Tunable semiconductor lasers have been listed in numerous critical technology lists for future optical communication and sensing systems. This paper summarizes a tutorial that was given at OFC '03. It includes some discussion of why tunable lasers might be beneficial, an outline of basic tuning mechanisms, some examples of tunable lasers that have been commercialized, and a discussion of control techniques. More extensive data is given for the widely-tunable sampled-grating distributed-Bragg-reflector (SGDBR) type of laser, including data for such lasers integrated monolithically with modulators to form complete transmitter front ends. A summary of reliability data for the SGDBR laser is also given. It is concluded that tunable lasers can reduce operational costs, that full-band tunability is desirable for many applications, that monolithic integration offers the most potential for reducing size, weight, power and cost, and that sufficient reliability for system insertion has been demonstrated.

Side-mode suppression and wavelength controltolerance for sampled grating based DWDM laser arrays

Sampled grating DBR (SGDBR) based laser arrays were demonstrated to be feasible for realizing monolithically integrated DWDM sources. In order to ease the post-fabrication wavelength control for SGDBR laser arrays, the influence of the sampling duty cycle and the difference of reflection peak spacing is analyzed and investigated experimentally for achieving the best side-mode suppression ratio (SMSR) of a SGDBR laser array. It is found that such type of laser arrays can have good tolerance on the mirror misalignment. We demonstrated arrays with uniform wavelength combs of 32 wavelengths in 0.8 nm wavelength spacing. Both high SMSR and accurate wavelength registration are achieved for all lasers in an array. We also demonstrated 16-wavelength laser arrays of 50 GHz spacing whose wavelengths are aligned to the ITU grid with single-electrode operation.

Postgrowth control of the quantum-well band edge for the monolithic integration of widely tunable lasers and electroabsorption modulators

We describe a quantum-well intermixing process for the monolithic integration of various devices, each with a unique band edge. The process involves a single ion implant followed by multiple etch and anneal cycles. We have applied this method to design and fabricate widely tunable sampled-grating distributed Bragg reflector lasers with integrated electroabsorption modulators. The devices employ three unique band edges, and demonstrate exceptional tuning, gain, and absorption characteristics.

Widely tunable EAM-integrated SGDBR laser transmitter for analog applications

A widely tuneable electroabsorption-modulated sampled-grating distributed Bragg reflector laser, integrated with a semiconductor optical amplifier is characterized for analog applications. The wavelength can be tuned anywhere from 1522 to 1573 nm. The suboctave spurious-free dynamic range (SFDR) is between 125-127 dBHz/sup 4/5/ measured at eight sampled wavelengths over the tuning range. The broad-band SFDR is in the range of 103-107 dBHz/sup 2/3/ limited by third-order intermodulation products or 95-98 dBHz/sup 1/2/, limited by second-order intermodulation products.

Monolithically integrated Mach-Zehnder interferometer wavelength converter and widely tunable laser in InP

The first monolithically integrated widely tunable wavelength converter, consisting of a sampled-grating distributed-Bragg-reflector laser (SGDBR) and an SOA-based Mach-Zehnder interferometer, is reported. The integration process requires only a single regrowth step. Static extinction ratios (electrical/optical) better than 18 dB and 13 dB, respectively, were measured over a 22-nm wavelength tuning range. Digital wavelength conversion at bit rate of 2.5 Gb/s was demonstrated to be error free, with 2.6-dB power penalty.

Widely tunable electroabsorption-modulated sampled-grating DBR laser transmitter

We report on a widely tunable transmitter based on a sampled-grating distributed Bragg reflector (SG-DBR) laser monolithically integrated with a semiconductor optical amplifier (SOA) and an electroabsorption (EA) modulator. Modulated time-averaged powers in excess of 5 dBm, RF extinction ratios >10 dB, and error-free transmission at 2.5 Gb/s for 350 km of standard single-mode fiber have been demonstrated across a 40-nm tuning range. In CW mode of operation, the module meets all long-haul system requirements for externally modulated laser sources: stability, power (>10 mW), RIN ( 100 yr for output wavelength stability and power across all channels.

Tunable sampled-grating DBR lasers using quantum-well intermixing

Widely tunable lasers are key components for wavelength division multiplexing fiber optic networks. They reduce cost in sparing, enable dynamic networking applications, and present opportunities for future monolithically integrated wavelength division multiplexing components. The sampled-grating distributed Bragg reflector (SGDBR) laser is ideal for these purposes. The authors present a centered quantum-well SGDBR laser which uses quantum-well intermixing in order to improve device characteristics over previous designs. The mode overlap is improved by 50% over the offset quantum-well design, improving the modal gain. Current injection tuning in the intermixed material is demonstrated for the first time; the maximum modal group index change was measured to be 1%.

Relative intensity noise measurements of a widely tunable sampled-grating DBR laser

The intensity noise of a sampled-grating distributed Bragg reflector laser with 50-nm tuning range and 45-dB side-mode suppression ratio has been measured. The resonance frequency, damping factor, and modified Schawlow-Townes linewidth are extracted from the noise spectra. At high output power, the relative intensity noise (RIN) of the laser is below the photodiode shot noise limit, which is -160 dB/Hz. The laser has uniform shot noise limited RIN properties along the whole tuning range. The maximum resonance frequency is 5.4 GHz at a bias current of 120 mA and the K factor is 0.58 ns.

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 2/sup 31/-1 word length at 2.5-Gb/s bit rate during transmission over 75-km of standard single-mode fiber.

Influence of mode competition on the fast wavelength switching of an SG-DBR laser

Because the sampled grating distributed Bragg reflector (SG-DBR) laser is among the most attractive sources for wavelength division multiplexing (WDM) systems, it is important and necessary to investigate its wavelength switching characteristics. This behavior will set the capability limits for reallocation in wavelength-routed optical networks. In this paper, that mode competition plays an important role in the wavelength switching dynamics of DBR-type tunable lasers is confirmed experimentally. By using a time-resolved spectrum technique, the loss-dependent mode competition behavior has been directly observed, for the first time, from measurements of wavelength switching on an SG-DBR laser.

Dynamic range of widely tunable sampled-grating DBR lasers

The dynamic range of sampled-grating distributed Bragg reflector lasers is investigated. The system noise is limited by the photodiode shot noise, which is below −160 dBm/Hz at normal bias current. The spur-free dynamic range is between 100–112 dB · Hz2/3. Both the noise and linearity are uniform over the whole tuning range of 50 nm, and are relatively insensitive to mode detuning.

Transmission matrix modelling of sampled-grating distributed Bragg reflector lasers

The transmission matrix model (TMM) has been used to simulate the tuning behaviour of a sampled-grating distributed Bragg reflector (SG-DBR) laser for the first time, to the best of our knowledge. The model is able to describe all details of the spontaneous emission spectrum below threshold and yields results in good qualitative agreement with experiment.

Frequency plan and wavelength switching limits for widely tunable semiconductor transmitters

As wavelength-division-multiplexing (WDM) channel spacing continues to decrease in size, and with the application of tunable lasers in dense wavelength-division-multiplexing (DWDM) systems, we demonstrate the ability of tunable semiconductor lasers to cope with demanding channel spacing and inevitable low frequency setting error. By finding the stable operating points of a single tunable laser at the desired frequencies, using advanced software a lookup table to drive the laser was generated. Once the drive currents to access 2000 channels with the laser are found, their frequency setting error and side mode suppression ratio (SMSR) were found. These results open up new possibilities for DWDM access networks as well as providing a limit of achievement for channel density in the network. Meanwhile, since the sampled-grating distributed Bragg reflector (SG-DBR) laser is among the most attractive sources for DWDM, it is important to investigate its wavelength switching characteristics. This behavior will affect wavelength routing and the capability limits for channel reallocation in future networks. We present new detailed experimental studies on a high-speed SG-DBR laser by using a Fabry-Perot interferometer technique adapted for the noncontinuous wave case. Measurements of fast intramodal (i.e., cavity mode) and intermodal (i.e., supermode) wavelength switching and insights into the device's dynamic behavior are obtained. Implications are given for transmitter design in dynamic wavelength routing and channel reallocation.

Design of sampled grating DBR lasers with integrated semiconductor optical amplifiers

High output powers and wide range quasicontinuous tuning have been achieved in a sampled-grating distributed Bragg reflector laser with an integrated semiconductor-optical-amplifier. Using an amplifier with a curved passive output waveguide to suppress back reflection, we have achieved a quasicontinuous tuning range of over 50 nm and peak output powers greater than +8 dBm. Optimizing the device structure and the sampled-grating mirror design has enabled tuning ranges of up to 72 nm in devices without amplifiers.

Widely tunable 1.55 mm lasers for wavelength division multiplexed optical fibre communications

Using criteria defined to compare the performances of several widely tunable laser structures reported in the literature, we point out a structure which presents a good trade-off between high performances and technological processing simplicity. We designed and realised this component, the Sampled-Grating Distributed Bragg Reflector laser. The tuning mechanism and the main characteristics of the component are then presented. A short review is made to compare these results to those measured on different widely tunable structures, and to propose the improvements needed for practical implementation of these lasers for Wavelength Division Multiplexed (WDM) optical fibre communications.

Dynamic analysis of mode-locked sampled-grating distributed Bragg reflector laser diodes

A mode-locked sampled-grating distributed-Bragg-reflector (SGDBR) laser diode for generating a train of light pulses at terahertz repetition rates is proposed with a numerical analysis based on a time-domain large-signal model. The device consists of three parts: the saturable absorber section which serves as a mode-locker, the gain section as an amplifier, and the SGDBR as a spectrum filter. It is predicted that spectrum filtering of the SGDBR along with passive mode locking due to the saturable absorber is effective in generating a train of transform-limited mode-locked pulses at a high repetition rate.