16-Channel 25 Gb/s Electroabsorption Modulated Tunable Multi-Wavelength DFB Laser Array Based on REC Technique

A 12-channel 100-GHz-spacing thermally tunable multi-wavelength DFB laser array is demonstrated based on reconstruction-equivalent-chirp technique with good single-longitudinal-mode property (SMSR > 50 dB) and small temperature tuning range (15.5 °C).

Multi-wavelength distributed feedback laser array (DFB-MLA) based tunable semiconductor lasers have been widely used owing to the high mode stability and simple wavelength tuning scheme. In this paper, we proposed and experimentally demonstrated a matrix-grating tunable DFB laser array. And the reconstruction-equivalent-chirp (REC) technique is utilized to simplify grating fabrication and realize precise control of the grating phase. Traditionally, the laser is tuned by thermal-electric cooler (TEC), with large power consumption, slow wavelength tuning capability, and added device. To improve the wavelength tuning speed of laser, we varied laser's injection current instead of adjusting TEC's temperature. In addition, we analyzed the thermal influence of submount on the laser and then chose the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> as the submount material for its low thermal conductivity and poor heat dissipation, resulting in wide wavelength tuning range via injection current. The DFB-MLA chip achieves a better tunable effect as the lasers can be tuned at 3.5-3.7 nm per channel from 50 to 120 mA with stable output power of over 3 mw as contrasted with the laser on the AlN submount being tuned at 1.4-1.5 nm per channel. And the chip has a side-mode suppressing ratio (SMSR) of over 35 dB and strong stability of wavelength in the repeated experiments. The proposed method may give a new way to realize the wide tuning range tunable DFB laser with a simple wavelength tuning mechanism in the future, especially for the applications of uncooled low-cost tunable lasers.

We propose and experimentally demonstrate a stable tunable multiwavelength laser employing a semiconductor optical amplifier (SOA) in conjunction with an opto-very-large-scale-integration (VLSI) processor. By uploading digital phase holograms onto the opto-VLSI processor, the amplified spontaneous emission of the SOA is arbitrarily sliced and injected back into the SOA to generate multiple lasing wavelengths with a linewidth of 0.5 nm. Experimental results demonstrate a tunable multiwavelength laser with a tuning range from 1528 to 1533 nm with power fluctuations of less than 0.5 dB.

Article Phase Errors Correction of OCDMA En-/decoders based on Reconstruction Equivalent Chirp Technique was published on March 1, 2010 in the journal Journal of Optical Communications (volume 31, issue 1).

Wavelength-swept laser is one of the most critical common components of fiber Bragg grating (FBG) sensors. However, a fast, stable, integrated and low-cost multi-channel wavelength-swept laser array is still unavailable. In this article, a multi-channel simultaneous wavelength-swept DFB laser array based on the reconstruction-equivalent-chirp (REC) technique is proposed and manufactured. The REC technology simplifies the fabrication process and greatly reduces the cost of the laser. The laser array contains 4 lasers in parallel with integrated heating resistance for thermal tuning to broaden the wavelength-tuning range. Each single-wavelength DFB laser introduces a π-phase shift structure, which is used to improve the single-mode performance of the laser. Meanwhile, the active multiplexer responsible for coupling and an optical amplifier (SOA) responsible for compensating the coupling loss of the laser are also integrated on the same chip. The driving circuits of the laser use FPGA to control the DAC chip to obtain precise current output and realizes continuous linear output of wavelength by changing the injection current size. The packaged laser module can realize a continuous wavelength-swept range of 2.4 nm per channel with the SMSR over 40 dB, achieving a simultaneous sweep of four channels with good scanning linearity and scanning speed. The work of this paper realizes the integration of linear wavelength-swept light sources, which creates the conditions for a low-cost, small-volume multi-channel sensing system in the future.

The service evolution and the rapid increase in traffic levels fuel the interest toward switching paradigms enabling the fast allocation of Wavelength Division Multiplexing WDM channels in an on demand fashion with fine granularities (microsecond scales). For this reason, in the last years, different optical switching paradigms have been proposed (Sabella et al., 2000): optical-packet switching (OPS), optical-burst switching (OBS), wavelength-routed OBS, etc. Among the various all-optical switching paradigms, OPS attracts increasing attention. Owing to the high switching rate, Semiconductor Optical Amplifier (SOA) is a key technology to realize Optical Packet Switches. We propose some Optical Packet Switch (OPS) architectures and illustrate their realization in SOA technology. The effectiveness of the technology in reducing the power consumption is also analyzed. The chapter is organized in three sections. The main blocks (Switching Fabric, Wavelength Conversion stage, Synchronization stage) of an OPS are illustrated in Section 2 where we also show some examples of realizing wavelength converters and synchronizers in SOA technology. Section 3 introduces SOA-based single-stage and multi-stage switching fabrics. Finally the SOA-based OPS power consumption is investigated in Section 4.

To enhance the functionality and flexibility of a multiwavelength fiber laser, characteristics such as the tunability of the lasing wavelength, the wavelength spacing and the number of channels should be investigated simultaneously. We have demonstrated a channel spacing and wavelength tunable multiwavelength fiber ring laser based on semiconductor optical amplifier and a novel tunable polarization-diversity loop configuration (PDLC)-based comb filter. The tunable PDLC-based comb filter would be composed of a polarization beam splitter and three wave plates (one quarter wave plate and two half wave plates) and a polarization differential delay line (DDL). Channel spacing can be controlled continuously by using a motorized polarization differential delay line. And wavelength can be simultaneously changed by controlling wave plates. The PDLC-based comb filter has the advantages of the input polarization independence and simple tunability. By employing the comb filter in the laser system, multiwavelength operation of up to 25 laser lines with the signal-to-noise ratio over 25 dB and 0.8 nm wavelength spacing has been demonstrated at room temperature. Also, we could achieve the increased output channel power of the laser while reducing the number of channels. The results show that the multiwavelength operation is even and stable. And we could achieve the output spectra of tuned wavebands with channel spacing of 1.6 nm and 0.4 nm when the semiconductor optical amplifier is driven with the injection current of 160 mA while adjusting a half-wave plate at each tuning set. As a result, the shift of lasing wavelength and wavelength spacing were continuously controllable in this system.

We discuss the design, fabrication, and performance of experimental multiwavelength laser array transmitters that have been used in the reconfigurable optical network testbed for the Optical Network Technology Consortium (ONTC). The experimental four-node multiwavelength network testbed is SONET/ATM compatible. It has employed multiwavelength DFB laser arrays with 4 nm wavelength spacing for the first time. The testbed has demonstrated that multiwavelength DFB laser arrays are indeed practical and reproducible. For the DFB laser arrays used in such a network the precise wavelength spacing in the array and the absolute wavelength control are the most challenging tasks. We have obtained wavelength accuracy better than /spl plusmn/0.35 nm for all lasers, with some registered to better than /spl plusmn/0.2 nm. We have also studied the array yield of our devices and used wavelength redundancy to improve the array yield. Coupling efficiencies between -2.1 to -4.5 dB for each wavelength channel have been obtained. It is achieved by using specially designed lensed fiber arrays placed on a silicon V-grooved substrate to exactly match the laser spacing. The transmitter consisted of a multichip module containing a DFB laser array, an eight-channel driver array based on GaAs IC's, and associated RF circuitry.

A multi-wavelength laser source is demonstrated with a semiconductor optical amplifier (SOA) as a gain medium. A multi-wavelength comb with equal spacing is achieved due to Fabry–Pérot modes of the SOA which oscillates in the ring cavity. A 100 m long photonics crystal fiber (PCF) is inserted in the ring cavity to provide a nonlinear gain by four-wave mixing (FWM) so that the output comb spectrum can be greatly broadened and flattened. The stability of the ring laser is also increased due to the efficient FWM phenomenon occurring in the PCF. The SOA-based laser can generate 35 lasing lines with equal spacing of 0.28 nm and extinction ratios of more than 30 dB at room temperature. The number of channels of the multi-wavelength laser can be controlled flexibly by changing the ratio of the coupler used in the ring cavity configuration as well as controlling the polarization state of the oscillating laser.

We fabricated a compact 10-Gb/s-wavelength tunable laser module by integrating a tunable DFB laser array and an InP-based n-i-n Mach-Zehnder modulator in one package. We developed a multichip assembly technology to realize high optical coupling efficiency and achieved a continuous-wave output power of +6.5 dBm. We demonstrated a full C-band 10-Gb/s optical duobinary transmission with a constant modulation voltage of 2.4 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> . And we achieved a 200-km single-mode-fiber transmission with a power penalty of less than 1.0 dB over the entire C-band range.

Since the underlying demand for network capacity can be satisfied only by extremely increasing transmission bit rate, processing speed, and switching capacity, it definitely will lead to increased power consumption of network nodes. Energy crisis is global crisis nowadays and it has brought up many problems. Power consumption is becoming a crucial issue in designing high-performance network devices. This paper studies the power consumption model of a kind of Optical Packet Switching (OPS) node based on Semiconductor Optical Amplifiers (SOA). Our results show that by dynamically adjusting the bias current of SOAs, the power consumption on an OPS node can be reduced considerably, especially when the traffic distribution across multiple ports is not balanced and inter-nodal distances vary. The total electrical power consumption can be cut off significantly. We also show the power consumption can be further reduced by jointly optimizing the thermoelectric cooler current.

Summary form only given. An overview is presented of the progress in design and characteristics of semiconductor optical amplifiers (SOA) for 1310, 1400 and 1550 nm operation in fiber optical transmission systems. The technology and performance of SOAs will be discussed with respect to optical gain, noise figure, saturation output power and polarization (in-) dependent behavior. The use of both strained quantum wells and bulk tensile material will be discussed in view of obtaining polarization independent behavior. Gain clamping in SOAs has been shown to improve the linearity performance especially for analogue signal transmission. The SOA technology has been demonstrated for optical pre-amplification, in-line application and optical booster applications. DWDM experiments using SOAs in up to 20 Gbit/s systems in short- and medium-distance transmission will be highlighted. Also, SOAs have been used in optical demultiplexing from 40 Gbit/s down to 10 Gbit/s RZ signals using its phase properties and in integrated photonic devices like multiwavelength lasers.

We will discuss in this presentation a novel and simple erbium-doped fiber laser configuration for multi-wavelength oscillation at room temperature, in which a few-mode fiber Bragg grating was used as the wavelength-selective component. This multi-wavelength laser can be switched between dual- and triple-wavelength operations by properly adjusting polarization controller in the cavity. By using stain- or temperature-induced few-mode fiber grating, we also demonstrate a tunable multi-wavelength laser based on the proposed scheme. This multi-wavelength laser has the advantage of simple configuration, high stability, low cost and stable operation at room temperature.

In this paper, we have proposed and demonstrated a multi-wavelength laser source based on a semiconductor optical amplifier (SOA) and optical filter module. The optical filter module is composed from a polarizer (P), polarization controller (PC), polarization maintaining fiber (PMF) and mirror. The multi-wavelength laser is generated by constructing SOA and optical filter module in a loop. The output wavelengths are determined by an optical filter module. The Experimental results revealed that a stable multi-wavelength lasing with 0.27 nm wavelength spacing is achieved at room temperature. Moreover, the proposed method is cost effective compared to the previously proposed schemes.

To realize a high-speed high-reliability wavelength switching at future WDM networks, we proposed the injection current/temperature cooperative control method of the tunable-distributed-feedback (DFB) laser array (TLA) for avoiding a large injection current, which is the primary cause of laser degradation. We successfully demonstrated a full-C-band wavelength switching within 124 ms by rapid increase of the injection current and following gradual decrease of the injection current to avoid laser aging. Compared to the conventional control method, the meantime to failure of the TLA in the proposed method is estimated to be extended by 44 times.