Iet Optoelectronics最新文献

This work proposes a design of a dynamic range adjustable laser ranging chip based on element sharing, which combines single photon avalanche diodes and direct time-of-flight (dToF) to address the uncertainty of detection distance in different usage scenarios of laser ranging technology. To achieve adjustable dynamic range of the chip, an element shared control logic circuit based on external control signals is designed and integrated, which can adjust the measurement dynamic range of the chip through external control signals, making it suitable for different usage scenarios. Moreover, when the dynamic range of the chip changes, the measurement resolution of the time-to-digital converter (TDC) in the chip can remain unchanged. Through the analysis of simulation results, it is found that the laser ranging chip designed in this work can adjust the dynamic range from 3 ns to 4.29 s based on external control signals at a resolution of 125 ps, with a reference clock signal input frequency of 20 MHz. The differential non-linearity (DNL) error of TDC is −0.22 LSB to 0.19 LSB, and the integral non-linearity (INL) error is −0.82 LSB to 0.52 LSB. The dynamic range adjustable laser ranging chip based on element sharing designed in this work provides a feasible solution to address the uncertainty of detection distance in laser ranging technology.

In this paper, continuous-wave and cavity-dumped Nd:YVO4 lasers are studied. Firstly, through theoretical analysis and numerical simulation, the output characteristics of a continuous-wave laser based on the magneto-optical effect are analysed using the rate equation. The continuous adjustment of output power and pump threshold power is realised using the magneto-optical effect to rotate the polarisation direction of laser. The theoretical simulation results show that the output power of the laser could be effectively controlled under different magnetic field intensities. On this basis, the authors explore the cavity-dumped laser system based on the magneto-optical effect. By adjusting the intensity of the magnetic field and rising edge time, the pulse width and waveform could be flexibly adjusted. The relationship between the magnetic field intensity in the low Q period and the spot radius of the pump and the signal beam and the output energy and the output pulse waveform is analysed. These research results lay a foundation for further optimising the design and application of magneto-optical effect lasers.

The authors aim to build a theoretical system for calibrating the position detection of a single quadrant photodiode (QPD) attached to 2D rotators and to suppress noise using a Sugeno-type fuzzy inference system. According to the results, if the original ANFIS network (NW_o) is trained under the conditions of resolution (rs_o), traing samples (N_o), and the possibility of random noise (p_o) and presented as {original, rs_o, N_o, p_o}, with the #X testing case presented as {case #X, rs_x, N_x, p_x}, case #X is expected to be the all-pass case of the two root-mean-squared error criteria under the conditions of rs_x ≥ rs_o and p_x ≤ p_o. Thus, the measurement accuracy is improved without tracking historical data. Furthermore, the two conditions indicate the limitations of the proposed ANFIS-based method. These conditions can be employed to save time and money. If a company produces many types of QPD rotators with different values of rs, the engineers can optimise the design to train the ANFIS network with only one case with the smallest rs and a larger p for all types of QPD rotators with any value of rs and p. This demonstrates the potential industrial application of the proposed method.

The cover image is based on the Article ANFIS-based controlled spherical rotator with quadrant photodiode to improve position detection accuracy by Bing-Yuh Lu et al., https://doi.org/10.1049/ote2.12127.

The authors examine the state of submarine cable systems and conditions affecting potential widespread deployment of new spatial division multiplexing technologies, such as multicore optical fibre. The authors address areas such as cable capacity requirements, techno-economic constraints, multicore fibre characteristics, and performance and other necessary technology advances.

2-core fibre for submarine cable is becoming the first commercial application of multi-core fibre, which should enable to expand the capacity beyond the current limitation of submarine cable size. For successful commercial applications of 2-core fibre, it is important to minimise the complexities in manufacturing, splicing, and fibre handling. The 2-core fibre design for minimum complexity is reviewed.

A coherent optical receiver digital signal processing (DSP) scheme is proposed based on spectral clustering, which utilises spectral clustering to cluster the signals outputted by the DSP. Compared to existing blind DSP algorithms for coherent optical receivers operating at over 100Gbps with PM-mQAM, the proposed scheme effectively suppresses various physical impairments, achieving lower bit error rates (BERs) at the same transmission distance, thus enabling longer transmission distances under the same forward error correction threshold. Furthermore, simulations of the proposed scheme on a 14GBaud PM-16QAM coherent optical transmission system show that, at a BER of 1.9E-2, the maximum transmission distance increases from 1700 to 2000 km, and at a BER of 3.8E-3, it increases from 700 to 900 km.

The authors present continuous wave (CW) high-power broad area and ridge waveguide lasers with laser emission at 626 nm at room temperature. For this, the authors employ GaAs-based diode lasers in the AlGaInP system for laser emission at 626 nm at room temperature. The laser structure is grown on three-inch wafers by metal organic vapour phase epitaxy. Broad area and ridge waveguide lasers are fabricated. Pulsed broad area laser characterisation on bar level shows laser operation at 20 C heat sink temperature. The authors measured peak lasing wavelengths as short as 625 nm and total maximum output power of both facets up to 1.4 W at an injection current of 2 A. Both, broad area and ridge waveguide lasers show laser operation and CW excitation at room temperature. The ridge waveguide lasers emit output powers of over 90 mW at 626 nm at a maximum injection current of 200 mA with a nearly diffraction-limited beam profile.

Amplification technologies needed for spatial division multiplexing (SDM) signal transmission have been reported, especially focusing on submarine systems, which have stricter requirements than terrestrial ones. As the first step of a large-scale commercialisation, 2-core un-coupled (UC) fibre production has already been announced. However, optical amplifiers for SDM signals are still under investigation because SDM amplifiers have various architectural possibilities, depending on the requirements to be considered in designing systems. The multicore erbium-doped fibre amplifier (MC-EDFA) architecture is classified from the viewpoint of the number of erbium-doped fibre (EDF) cores and its pumping method. Core pumped MC-EDFA is more compatible with the conventional single-core fibre (SCF)- based system and more mature than cladding pumped MC-EDFA. However, cladding pumped MC-EDFA has a unique feature of collective amplification of all cores in a single multicore fibre (MCF) and the potential of large-scale integration of amplification cores in a single package. For a feasibility study, a C-band 19-core cladding pumped MC-EDFA prototype is fabricated using a 19-core isolator. A half volume of the equivalent conventional single-core (SC-) EDFA is successfully demonstrated. One unique feature of UC-MCF is bidirectional (BD-) transmission using a single UC-MCF. Signal transmission direction can differ from core to core. This feature is useful for efficiently accommodating traffic of asymmetric communication data and expanding transmission capacity at a constant transmission distance. A C-band 7-core cladding pumped BD-MC-EDFA prototype is fabricated for the bidirectional MCF transmission line. Experimental results show transmission capacity was expanded by 17% using the prototype when bidirectional signal assignment was adapted. Towards practical use, optical components suitable for MC-EDFA need to be developed to draw out potential advantages of SDM technologies.

Free space optical communication (FSO) has become a popular research direction due to its high bandwidth, easy deployment, and inherent security. Its channel state is unstable because of atmospheric environment, especially in long-distance ground transmission system. Interleaving combined with forward error correction coding (FEC) have been utilised to improve the stability of system. However, there is little detailed experimental results of deep interleaving combined with FEC under different atmospheric turbulence intensity over long-distance FSO system. A deep interleaving with FEC method was designed and implemented on a 7 km long online experiment. The performance of different depth interleaving is analysed under weak and strong atmospheric turbulence state. The experiment results show that deep interleaving performs better under weak turbulence for the larger correlation factor of the channel and the outage probability of the system with deep interleaving can be greatly reduced.