Direct Modulation Laser Diode Research Articles

Direct-modulated active mode-locking optoelectronic oscillator for microwave frequency comb signals

Abstract The optoelectronic oscillator (OEO) has been widely investigated to generate ultrapure microwave signals. For many applications, microwave signals with large bandwidth and multiple frequency bands, such as broadband microwave frequency comb (MFC) signals, are also needed. Conventional MFC signals are generated by active mode-locking OEO (AML-OEO) using devices such as Mach–Zehnder modulators (MZM) and delay fibers, which make the system structure more complicated and take a long time to build up stable oscillation at an oscillation mode. In this paper, A direct-modulated AML-OEO (DM-AML-OEO) is demonstrated with the advantages of compact design, cost-effectiveness, and straightforward integration. Mode-locked pulses are generated by direct-modulated Laser Diode (LD) which have low-phase noise. Furthermore, different comb spacings of MFC signals can be readily attained by adjusting the frequency of the active modulation signal (AMS) while supermodels are confined. In the experiments, the DM-AML-OEO produced MFC signals that exhibited a central frequency of 718 MHz and a frequency spacing of 100 kHz.

Optical switch by direct modulated laser diode using fiber laser for pulse picking

Optical switch by direct modulated laser diode using fiber laser for pulse picking

A Simple WDM-PON Architecture Together With Private Interconnected ONUs

In this paper, we present and investigate a wavelength-division-multiplexing passive optical network (WDM-PON) with symmetrical 28 Gbit/s on-off keying (OOK) access signals and 3 Gbit/s virtual private network (VPN) link between the optical network units (ONUs) simultaneously. To achieve the VPN connection, a ring-based network architecture is designed to link every ONU. Here, a direct modulation laser diode (LD) of 1311.6 nm wavelength is applied in ONU for VPN transmission to separate from PON network. In the investigation, the fiber and free space optical communication (FSO) based connections are also exploited to connect every ONU. In addition, the corresponding signal behaviors of WDM-PON and VPN networks are also analyzed and discussed.

External Modulation Method for Generating Accurate Linear Optical FMCW

Frequency modulation continuous wave (FMCW) lasers are key components in modern optical imaging. However, current intracavity modulation lasers do not exhibit low-frequency jitter rate and high linearity due to the inherent relaxation oscillations. Although this may be compensated in a direct modulation laser diode using an optoelectronic feedback loop, the available sweep speed is moderately small. In this letter, a special external modulation method is developed to improve the performance of FMCW. Since only the first sideband optical field is used during the entire generation process, phase noise is kept to a minimum and is also independent of the sweep speed. We demonstrate that the linearity and jitter rates do not deteriorate appreciably when the sweep speed is changed over three orders of magnitude, even up to the highest sweep speed of 2.5 GHz/ $\mu \text{s}$ .

Selective delivery of broadband wireless and wired services in an integrated ROF-PON system using dual-sideband optical carrier suppression

Selective delivery of gigabit-per-second wireless and wired services is demonstrated in an integrated fiber-wireless access network using the millimeter-wave (mm-wave) radio-over-fiber (RoF) system employing the dual-sideband optical carrier suppression technique. A dual-electrode Mach-Zehnder modulator is used in this technique to generate 40 GHz carrier to distribute 1.25 Gbps data via direct modulation (DM) over a 20 km RoF system. The results show that selective signal delivery can be achieved using a low-cost DM laser diode drive current of 20 mA. The advantage of the proposed system is that it provides versatility to control the gigabit-per-second (Gbps) signal delivery in an integrated ROF-PON system with a common high frequency oscillator shared for the whole system. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1768–1773, 2016

Efficient adjustment of the RF parameters of directly modulated laser diodes with ‘RF’ light-current parameters

An efficient method of adjusting the RF parameters of directly modulated laser diodes (LDs) is presented. By using the light-current parameters estimated from initial RF measurements, the new bias and modulation currents are obtained self-consistently for the target extinction ratio and average optical power. Experiments performed using distributed feedback lasers show that this adjustment method works efficiently, bringing the initial RF parameters very close to the target values within a couple of iterations. This method can be useful in manufacturing where there is a need to adjust the RF performance of the direct-modulated LDs to a desired specification.

Multiwavelength monitoring by dithering temperature of directly-modulated laser diodes

A multiwavelength monitoring technique for wavelength division multiplexed passive optical network systems is proposed. This technique removes the need to place one optical filter at each transmitter and so makes their configuration more compact. To generate a wavelength monitoring signal, the temperature of each directly-modulated laser diode is dithered by a sinusoidal signal. Experiments confirm the feasibility of this technique.

Compensation for Nonlinear Distortion of Optical Transmitter with Predistortion

The paper studies the nonlinear distortion of direct modulated laser diode applying to AM-VSB lightwave CATV systems from the viewpoint of rate equations and designs a predistortion circuit in an easier way. It is shown that CSO and CTB in 60 PAL channels have been improved obviously.

1-Gb/s two-beam transimpedance smart-pixel optical receivers made from hybrid GaAs MQW modulators bonded to 0.8 μm silicon CMOS

We have made two-beam smart-pixel optical receivers using a hybrid attachment of GaAs-AlGaAs multiple quantum-well (MQW) pin devices to foundry-fabricated 0.8-μm linewidth CMOS circuits. Results from a repeater in which receiver output is coupled to a transmitter circuit driving a differential pair of MQW modulators are reported. When tested with high-contrast, directly-modulated laser diodes, an optical energy of 26 fJ (-21.5 dBm) in each beam is required to obtain a bit error rate of 1×10/sup -9/ at 622 Mb/s, and operation at this error rate is observed to 1 Gb/s. The described receiver (one of several we have made) has three amplification stages, with the first being of the transimpedance type. The reported receiver fits easily within a 45×25 μm area, and the entire repeater circuit draws about 2 mA from a 5-V power supply, with the transmitter accounting for about 20 percent of the total.

Perturbation analysis of bistability and period doubling bifurcations in directly-modulated laser diodes

Resonance frequency shift, bistability, and period doubling bifurcations in directly modulated semiconductor lasers are accounted for by applying multiple scale expansions to the rate equations that take into account spontaneous emission and gain saturation. Explicit algebraic expressions of parameter ranges for resonance frequency shift, bistability, and period 2 and period 4 oscillations are derived, and they are compared with results of numerical calculations. Physical mechanisms of resonance frequency shift and period doubling bifurcations are also explained.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>