Chaos optical time domain reflectometry (chaos OTDR) has an advantage of high spatial resolution without tradeoff of measure distance by utilizing correlation detection based on broadband chaotic laser. However, achieving a high spatial resolution usually requires a wideband photodetector and a high-speed data acquisition card. In this letter, we propose a significant-bit correlation method to improve spatial resolution of chaos OTDR instead of increasing hardware bandwidth. In this method, the reference and echo chaotic signals are quantized with multi-bit ADC, and some least significant bits (LSBs) are extracted to construct new time series for calculating cross correlation. Our experimental results demonstrate that the spatial resolution is significantly enhanced as the number of LSBs decreases. Under a detection bandwidth of 200 MHz, the spatial resolution is approximately improved 5 times from 21 cm to 4 cm with 6-LSBs correlation. The improvement of spatial resolution is attributed to bandwidth enhancement caused by LSBs extraction.

The dynamics of mutually coupled nano-lasers subject to direct current modulation has been analyzed using rate equations, which include the Purcell cavity-enhanced spontaneous emission factor F and the spontaneous emission coupling factor β. Subject to two different modulation frequencies, the mutually coupled nano-lasers display two general types of response. The laser with the lower modulation frequency simply exhibits a response at that modulation frequency. Thus, we term a zero cross-talk response. On the other hand, at higher modulation frequencies the system displays a variety of dynamical responses which, in addition to zero cross-talk, includes a range of behaviors, which are classified from low cross-talk through to a complicated non-linear response. The precise behavior being dependent on the depth of modulation and the laser bias currents. The operational significance of the zero cross-talk regime is that it permits access to a simple periodic response at the modulation frequency. With a view to utilization, it is established that the region of zero cross-talk response enlarges with increasing modulation depth and increasing bias current. In this way, conditions are established, in which the lasers may act independently. The propensity for zero cross-talk response under stronger driving is consistent with previous analysis wherein modulated nano-lasers may have superior characteristics in the large-signal regime.

A high-resolution leaky coaxial cable (LCX) sensor for perimeter intrusion detection is proposed and experimentally demonstrated. In our proposed sensor system, a wideband Boolean-chaos signal is used as the probe signal, and a pair of leaky coaxial cables (LCXs) is applied for transmitting the probe signal and receiving the echo signal, respectively. By correlating the chaotic echo signal with its delayed duplicate and comparing the correlation traces before and after intrusion, the intruder can be accurately located. Experimental results demonstrate the proposed sensor can simultaneously detect multiple intruders. The range resolution reaches 30 cm, whilst the dynamic range can achieve 50 dB. In addition, this sensor possesses the excellent anti-interference performance to the noise and uncorrelated chaotic signal, which makes it show robust performance in the detection environment with noise or multiple chaotic LCX sensors cooperation.

The dynamics of mutually coupled nano-lasers has been analyzed using rate equations which include the Purcell cavity-enhanced spontaneous emission factor F and the spontaneous emission coupling factor β. It is shown that in the mutually-coupled system, small-amplitude oscillations with frequencies of order 100 GHz are generated and are maintained with remarkable stability. The appearance of such high-frequency oscillations is associated with the effective reduction of the carrier lifetime for larger values of the Purcell factor, F, and spontaneous coupling factor, β. In mutually-coupled nano-lasers the oscillation frequency changes linearly with the frequency detuning between the lasers. For non-identical bias currents, the oscillation frequency of mutually-coupled nano-lasers also increases with bias current. The stability of the oscillations which appear in mutually coupled nano-lasers offers opportunities for their practical applications and notably in photonic integrated circuits.

We present a theoretical study of the nonlinear dynamics of a long external cavity delayed optical feedback-induced interband cascade laser (ICL). Using the modified Lang–Kobayashi equations, we numerically investigate the effects of some key parameters on the first Hopf bifurcation point of ICL with optical feedback, such as the delay time (τ_f), pump current (I), linewidth enhancement factor (LEF), stage number (m) and feedback strength (f_ext). It is found that compared with τ_f, I, LEF and m have a significant effect on the stability of the ICL. Additionally, our results show that an ICL with few stage numbers subjected to external cavity optical feedback is more susceptible to exhibiting chaos. The chaos bandwidth dependences on m, I and f_ext are investigated, and 8 GHz bandwidth mid-infrared chaos is observed.