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An optical mode cross-connect (OMXC) between fundamental modes using multimode interference coupler MMI with high performance has been proposed in this paper. These basic modes can be transmitted in turn or at the same time toany input and be able to select arbitrary outputs. The following inputs can only select the remaining outputs, so this process will not cause bottlenecks in the circuit. In order for the signals to be flexibly switched to the outputs without conflict, the phase shifters will be used to control their lightpaths. Through the BPM-3D beam propagation method, we have shown the flexible switching process between the input and output ports of the device with insertion loss always smaller than 1.8 dB in the range of wide wavelength from 1.53 µm to 1.565 µm. Specifically, attenuation only reaches -0.5 dB at the central wavelength of 1.55 µm. In addition, the crosstalk is always in a very small range from -44 dB to -24 dB for the entire band considered above. With these advantages, it is a promising device for optical mode processing circuits in the MDM system.

We propose a compact silicon-on-insulator based device which is capable of arbitrarily converting optical modes TE $_\text{i}$ to TE $_\text{j}$ (i, j = 0, 1, 2, 3). The device consists of two symmetric 1 × 4 Y-junction couplers connected back-to-back with a 4 × 4 multimode interference coupler (MMI). While the two 1 × 4 Y-junction couplers are designed to divide and combine modes at the input and output of the device, the 4 × 4 MMI coupler is used to direct signals from its inputs to suitable outputs. The conversion of a pair of modes is decided by four phase shifters located at the input and output of the MMI coupler. Through beam propagation method (BPM) with effective index method (EIM) simulations, we show that by setting the phase shifters to 0° or 180°, 16 different conversion pairs of input-output modes (TE $_\text{i}$ –TE $_\text{j}$ ) are successfully realized with a mode conversion efficiency larger than 98% and a crosstalk smaller than −30 dB within a wide wavelength range from 1530 nm to 1565 nm.

Noise-like artifacts, which are caused by incomplete and randomly sampled data, spread over the whole ambiguity domain, and thus seriously obscure the true time-frequency signature of the data. In this paper, a new design for the signal-dependent adaptive kernel is proposed, which is robust with missing data. The method relies on the properties of chirps whose auto-terms only reside in a fixed half of the ambiguity domain. The important thing is that this half excludes the Doppler axis, where the chirps’ noise-like artifacts concentrate. By cutting out this region when performing the optimization problem, a better signal-dependent kernel for chirps is obtained, which efficiently suppresses not only the cross-terms but also the missing sample artifacts. Moreover, since any windowed non-stationary signals can be approximated as a sum of chirps, the proposed approach can be applied to other types of non-stationary signals. It is shown in the simulation that our method outperforms other reduced interference time-frequency distributions of incomplete observations.

We propose a 4x4 small size optical mode switch applied for photonics integrated circuits. The proposed device consists of four Multimode Interference (MMI) couplers based on silicon material and ten phase shifters appropriately placed between ones. The fundamental modes at the input are selectively switched to the desired outputs by controlling the phase shifters. Through a beam propagation simulation method (BPM) combined with an effective index method (EIM), we evaluate the efficiency of optical conversion when transmitting signals from any input to arbitrary outputs of the device. At the center wavelength of 1.55 µm, the insertion loss is always less than 0.3 dB, and the crosstalk is always from -80 dB to -30 dB in the entire C-band.

We design a 4×4 single-mode optical switch which is capable of switching four fundamental modes from four input ports to any of the four output ports. The proposed device consists of two 4×4 multimode interference couplers on an SOI platform with 220 nm thick Si layer. Mode signals selected at the desired output were determined by four phase shifters placed between two MMIs. Through numerical simulation method BPM combined with EIM method, we evaluate optical conversion efficiency when transmitting optical mode signals at any input and measuring optical power at outputs. At 1550 nm central wavelength, insertion loss is always less than 0.1 dB and below 1.6 dB in the entire C band. Furthermore, the crosstalk is always from -110 dB to -50 dB in a range of band of 35 nm.

In this paper, we introduce a structure can generate simultaneously three lowest optical modes TE 0 , TE 1 and TE 2 based on SOI platform. This device is built on two tridents and one Multimode interference (MMI) couplers. It is designed using 3D beam propagation method (3D-BPM) combined with effective index method (EIM). The simulation results show that the proposed device can operate in a wide wavelength range up to 140nm covering whole C and almost of L and S bands with low insertion loss, about -0.23 dB at the central wavelength of 1550 nm. Manufacturing tolerances of the device is rather large. In addition, the small footprint (5 µm×506 µm) makes the device not only compatible with the current CMOS manufacturing technology but also suitable with high bitrate applications of photonic integrated circuits inside MDM-WDM systems.

In this work, a photonic-silicon-based 1✕3 reconfigurable simultaneous three-mode selective router has been demonstrated by the proof-of-concept. The device can be flexibly controlled to route three input modes of TE0, TE1, and TE2 to three outputs by utilizing three controllable Ti thermo-optic phase shifters as drivers. The proposed router is constructed from a Ψ -junction coupler and two kinds of 3✕3 multi-mode interference (MMI) couplers. The proposed device can attain low insertion loss smaller than 5 dB and crosstalk below −20 dB in broadband of 40-nm thanks to the numerical simulation-based optimization. Furthermore, the proposed router has relatively large fabrication tolerances of width and height and consumes a low electric power consumption. The proposed device is reconfigurable for simultaneous three guided modes, and thus, leading to a promising potential to widely apply for broadband optical signal processing in the mode-division multiplexing systems.

In mode-division multiplexing (MDM) networks, converting modes back and forth between a higher-order mode and a lower-order mode plays a vital role in improving network capacity and flexibility. This paper presents a spatial optical mode conversion supporting three modes based on two Ψ -junction couplers and two multi-mode interference couplers (MMIs). The proposed device can arbitrarily convert a TEi mode to a TEj mode (where i, j = 0, 1, 2) by setting three phase-shifters at 0 or 180 degrees, which are introduced at the Ψ -junction and MMI couplers. Through numerical simulations using the spatial three-dimensions beam propagation method (3D-BPM), the mode converter shows a high conversion efficiency with the insertion loss smaller than 0.2 dB and the crosstalk below −20 dB at the center wavelength of 1.55 μm. The device works effectively in C band, partially in S and L bands within a wideband up to 80 nm. We believe that the proposed device would be a potential platform for applications in MDM networks and photonic integrated circuit systems.

This paper proposes a new design of two-mode three-port optical mode router for mode division multiplexing systems. The device consists of a Mach-Zehnder interferometer (MZI) and a multimode interferometer (MMI), which utilizes silicon material for photonic integrated circuits (PIC). By setting appropriate values for the two butterfly-shaped phase shifters (PSs) at MZI and MMI, the input mode, either transverse electric (TE) modes TE0 or TE1, can be routed to the desired output among the three output ports. The device is designed and optimized via three-dimensional beam propagation method (3D BPM). The proposed device achieves very low insertion loss and small cross-talk, which are less than 0.4 dB and -24.5 dB, respectively, over the whole C band.

We propose a compact device that can (de)multiplex the two lowest polarization-insensitive modes (TE0 / TM0 and TE1 / TM1) by using silicon-on-insulator substrate. The proposed device consists of a Y-junction coupler and a 2 × 2 multimode interference coupler. We use both beam propagation method and effective index method to optimize and simulate this device. The simulation results show the advantages of our device, such as large wavelength range up to 95 nm, low insertion loss, large fabrication tolerances, and small footprint.

Ultra wideband (UWB) system using multi antennas and time reversal (TR) possesses capability of multiuser system. Each user with long channel response signature is exploited for multiple access problems. If UWB channels are independent, the multi antenna UWB system shows both capacity and diversity gain. However, due to correlation between antennas, the performance of system degrades. In this paper, the channel capacity of multi user multi antenna TR-UWB system and the difference between the impact of transmit correlation and that of receive correlation on the system are derived. Channel capacity of system is significantly improved when number of using antennas increases in a acceptable range of the correlation coefficient. If the correlation of antennas is considered, at high correlation, the capacity reduces up to 60% in comparison with capacity if without correlation.