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This paper reports an uncooled transmitter system using a digital super-mode (DS) distributed Bragg reflector (DBR) tunable laser, which is able to act as an athermal, wavelength agnostic transmitter suitable for wavelength division multiplexed (WDM) passive optical network (PON) applications. An open-loop laser current control algorithm is designed to compensate autonomously for wavelength drift, thus allowing constant operating wavelength to be achieved regardless of ambient temperature. An improved wavelength accuracy of ±3 GHz is achieved when using low bandwidth feedback from the central office using information from a centralized shared wavelength locker. The entire laser start-up, channel selection and subsequent wavelength control is autonomous and has been implemented on micro-controllers and field programmable gate arrays. We demonstrate a three channel WDM-PON system comprising an uncooled packaged DS-DBR laser in the presence of two neighboring interfering channels. Error free transmission over 40 km single mode fiber of 10 Gb/s externally modulated NRZ data, is achieved for each of 48 C-band channels on the 100 GHz ITU grid. Successful athermal operation is demonstrated by sweeping the ambient temperature of the laser from 15 to 70 °C with a maximum wavelength deviation for any channel of no more than 0.1 nm.

A range sidelobe suppression method is proposed for frequency diverse multiple-input multiple-output (FD-MIMO) sonar imaging. Unlike traditional methods which suppress cross-correlation functions (CCFs) between transmitting waveforms as low as possible, we use band overlapped frequency diverse continuous wave (FDCW) pulses to obtain relatively high CCFs. We point out that these relatively high CCFs can fill the band gap between auto-correlation functions (ACFs) between neighboring FDCW pulses, thereby showing an ability of reducing the spectrum leakage. Furthermore, we apply an amplitude weight vector to these FDCW pulses to further reduce the spectrum leakage and hence, produce much low range sidelobes. Via theoretical analyses and numerical simulations, we show that the proposed method can produce a high-resolution range profile as well as a low range sidelobe level.

A high angle and range resolution imaging method using a double-ping frequency diverse multiple-input multiple-output (MIMO) sonar is proposed. The proposed MIMO sonar is composed of a uniform linear array (ULA) and two transmitting elements located at the two ends of the receiving ULA. The interelement spacing of the two transmitting elements is equal to the produce of the inter-element spacing and the element number of the receiving ULA. We show that such array configuration is able to ensure a high angle resolution without increasing the array physical size. At the same time we use a pair of frequency diverse linear frequency modulation (FD-LFM) pulses to achieve a high range resolution. Based on the array configuration and the transmitting waveforms, we give the double-ping signal transmitting mode and the echo processing procedure. Via numerical simulations we show that the proposed double-ping MIMO sonar imaging method can improve the angle and range resolutions simultaneously.

We demonstrate a 3×10Gb/s uncooled MIMO DWDM system using uncooled DFB lasers with real-time crosstalk cancellation, allowing separate lasers to operate at different temperatures. Adaptive laser bias control is applied to ensure adequate channel separation.

We describe the performance of an optimized high-temperature DS-DBR laser used as an uncooled WDM source. Constant wavelength output with less than 6GHz error without mode-hopping is shown for C-band channels from 70-90 °C.

A proof-of-principle demonstration of a multiple input-multiple output (MIMO) dense wavelength division multiplexing (DWDM) system is reported. It uses standard uncooled distributed feedback (DFB) lasers with intensity modulation-direction detection (IM-DD), in which the temperature of each laser is allowed to drift independently within a 50°C temperature range. A feedback-based laser bias control algorithm is introduced to guarantee acceptable wavelength spacing and a post-photodetection minimum mean square error (MMSE) decoder is applied to cancel the inter-channel crosstalk. The relative sensitivity of the MIMO receiver in both a random laser temperature drift scenario and a worst case scenario are investigated by simulations in MATLAB. Experimental results for a 40-channel × 12.5 Gb/s DWDM system transmitting over 28 km of single-mode fiber with worst possible wavelength distribution prove the feasibility of the technique.