Fig 5 - uploaded by Xinliang Zhang
Content may be subject to copyright.
Source publication
We propose a novel scheme that combines a polarization-beam splitter (PBS) and a 90$^{\circ}$ hybrid into a single device to demodulate the dual-polarization quadrature phase-shift keying (DP-QPSK) signal by introducing a photonic crystal structure into a 4$\,\times\,$ 4 multimode interference coupler. Since no separated PBS is utilized, the demodu...
Contexts in source publication
Context 1
... is used After designing the 4 4 MMI, it is crucial to design the PC structure as required. In this paper, we design the PC structure with a hexagonal pattern of air holes (with a period of ) in the multimode section. In order to realize the TE-transparent PC, the radius of the air hole is . The bandgap diagram for such a PC structure is shown in Fig. 5. Such a PC structure was found to have a bandgap in the spectral range for TM polarization as shown in Fig. 5. For the communication wavelength m, we set which falls inside the spectral range; then, we get the PC period m. We can get the wavelength range that the TM-pol cannot pass through. The length of the PC is chosen to be six ...
Context 2
... design the PC structure with a hexagonal pattern of air holes (with a period of ) in the multimode section. In order to realize the TE-transparent PC, the radius of the air hole is . The bandgap diagram for such a PC structure is shown in Fig. 5. Such a PC structure was found to have a bandgap in the spectral range for TM polarization as shown in Fig. 5. For the communication wavelength m, we set which falls inside the spectral range; then, we get the PC period m. We can get the wavelength range that the TM-pol cannot pass through. The length of the PC is chosen to be six periods to ensure large enough reflection for TM-pol. And the width of the PC should be m m periods to cover the ...
Similar publications
We propose and demonstrate an optical arbitrary waveform generator and high-order photonic differentiator based on a four-tap finite impulse response (FIR) silicon-on-insulator (SOI) on-chip circuit. Based on amplitude and phase modulation of each tap controlled by thermal heaters, we obtain several typical waveforms such as triangular waveform, sa...
We present the design and analysis of a Ka-band (26.5–40 GHz) CMOS quadrature coupler (QC) and four Ka-band CMOS power dividers. To reduce the chip area of these devices, spiral coupled-line- based structure (or spiral QC-based structure) is adopted. A QC on 90 nm CMOS (with top metal thickness of 3.4 μm) is designed. The QC achieves phase differen...
We experimentally demonstrate a 4 × 4 microring modulator matrix integrated with the asymmetrical directional couplers based mode multiplexer and de-multiplexer photonic circuit for on-chip optical interconnect. The inter-mode optical crosstalk of the device is less than −20 dB in the wavelength range from 1525 nm to 1565 nm. Data transmission with...
Recent developments of photonic integrated circuits for the mid-infrared band has opened up a new field of attractive applications for group IV photonics. Grating couplers, formed as diffractive structures on the chip surface, are key components for input and output coupling in integrated photonic platforms. While near-infrared optical fibers exhib...
We propose a novel power splitter (or divider) comprising two back-to-back quarter-wavelength (λ/4) coupled lines (i.e. coupler). To improve the isolation between the output ports (i.e. ports 2 and 3), an isolation resistor R is included. Three power dividers are designed and implemented. To enhance the reflection coefficients, and S21 and S31 and...
Citations
... This device exhibited a modulation bandwidth of 17.5 GHz, while its electro-optic modal volume was only 0.58 μm 3 [34]. In 2012, Xiang et al. proposed an ultracompact dual-polarization quadrature phase shift keying (QPSK) demodulator by incorporating a 4 × 4 PCW multimode interferometer and a polarization beam splitter [35]. The demodulation speed of QPSK signal in coherent optical communication is significantly improved. ...
... Optical hybrids that scale the usable bandwidth to match the range of photodetectors can enable new applications. Most of those 90 • optical hybrids that have been reported to operate over a broad spectrum are based on optical waveguides [13][14][15][16][17][18] and smooth phase masks [19]. Among fabricated hybrids reported so far, the largest bandwidth is 390 nm (1260-1650 nm) by using the multiplane light conversion technique in the experiment [19]. ...
We design a broadband free space $2 \times 4$ 2 × 4 90° optical hybrid over a spectral window of 1000–1200 nm and 1470–1650 nm and verify the feasibility of the scheme experimentally. The hybrid consists of three broadband polarization beam splitters, an achromatic $\lambda /4$ λ / 4 wave plate, and three achromatic $\lambda /2$ λ / 2 wave plates. The fabricated hybrid exhibits a good quadrature phase response with an interchannel imbalance of 0.93–1.07 and a low phase deviation of less than 0.2° under the typical communication wavelengths of 1064 nm and C-band. The experimental results of the heterodyne method show that the proposed hybrid can effectively solve the wavelength incompatibility problem in satellite laser communication and realize interconnection at different wavelengths. The designed hybrid (without coupling) has a measured insertion loss of no more than 7.34 dB at 1064 nm and C-band. A high-speed transmission experiment with BPSK format has been conducted to verify the performance of the assembled device.
... There are two special designs different from the integrated coherent balanced receivers reported in previous works [3][4][5][6][7][8][9][10][11][12][13]. First, different from the optical hybrids mainly realized using the MMI couplers based on traveling wave interference [3][4][5][6][7][8][9][10][11][12][13]28], the optical hybrid in our scheme is based on the coherent mechanism of standing wave, where it can generate the constructive interference light at antinodes and the destructive interference light at nodes of standing wave. Second, the waveguide-integrated GPD is used as an ultrafast SDPD, instead of the conventional BPDs based on PIN photodiodes in a coherent receiver. ...
In this paper, we propose a novel scheme to integrate an optical hybrid based on standing wave with graphene photodetector (GPD). Different from optical hybrids based on multimode interference (MMI) couplers, the proposed optical hybrid can be miniaturized by constructing a standing wave field in a silicon strip waveguide. The waveguide-integrated GPD with symmetric electrodes is adopted as an ultrafast self-differential photodetector (SDPD), instead of conventional balanced-photodetectors (BPDs) based on PIN photodiodes in a coherent receiver. By placing two sysmmetric interdigitated electrodes of the SDPD at nodes and antinodes of the standing wave, it is convenient to realize the integration of the proposed optical hybrid with the graphene-based SDPD, which can effectively reduce the complexity of a coherent receiver and meet future demand for wide bandwidth. The finite-difference time-domain (FDTD) method was used to calculate optical absorption for demonstrating operation feasibility. Finally, device bandwidth and effective responsivity have been discussed. In theory, our scheme would provide a feasible way to realize a high-speed compact coherent receiver. CCBY
... As the structures based on the MMI effect fulfills all of above requirements better than alternatives, there has been a growing interest in the application of MMI effect for developing the optical passive components [7][8][9]. Recently, MMI has been paid more and more attention due to its simple principle, and the property of integrating convenience, especially the compatibility of the organic material and the semi-conductor [10]. MMI couplers are extensively utilized in optical switches [11]. ...
The multimode interference (MMI) switch is a versatile component for photonic signal processing applications. A 4×4 silica-on-silicon (SOS) all-optical MMI switch design is presented in this paper. This structure is based on two cascaded 4×4 MMI couplers and phase compensation arms. First a 4×4 MMI coupler is designed using self-imaging principle and then it is optimized for minimum loss, uniformity and maximum power factor using improved self-imaging principle, as weakly guiding features of SOS waveguides are quite different from the strongly guiding features considered in the self-imaging principle. Mode propagation analysis (MPA) and beam propagation method (BPM) simulation has been used to analyze the MMI coupler structure performance. This optimized MMI couplers are then cascaded by using phase compensation arms; from the calculation of relative phases of MMI sections the phase compensations are obtained. Numerical simulation results of the designed switch consequences a better device performance with a loss of 1.03dB and crosstalk level of less than -20dB.
... Among all these multiplexing techniques, the polarization division multiplexing (PDM) has attracted more and more interest as it can double the SE by carrying two independent data streams on two orthogonal polarization states [4]. Although many previous reports have proposed and demonstrated the integrated transceivers for the PDM signal modulation and detection [5][6][7][8], there is few previous report on the corresponding PDM signals processing using the silicon based integrated devices. Only a few schemes demonstrated the relative all optical PDM processing utilizing the discrete devices [9][10][11]. ...
We propose and fabricate a novel circuit that combines two two-dimensional (2D) grating couplers and a microring resonator (MRR). According to the polarization states, one 2D grating coupler first splits the input signals into two orthogonal paths, which co-propagate in the loop and share a common MRR, and then the two paths are combined together by the other 2D grating coupler. The proposed circuit is polarization insensitive and can be used as a polarization insensitive filter. For demonstration, the wavelength division and polarization division multiplexing (WDM-PDM) non return-to-zero differential-phase-shift-keying (NRZ-DPSK) signals can be demodulated successfully. The bit error ratio measurements show an error free operation, reflecting the good performance and the practicability.
... With all these multiplex techniques, the PDM has attracted more and more interest recently as it can double the SE by carrying two independent data streams on two orthogonal polarization states [4]. Although many previous reports had proposed and demonstrated the integrated transceivers for the PDM signal modulation and detection [5][6][7], to the best of our knowledge, there is no previous report on PDM signals processing using the Si-based integrated devices, and only a few schemes demonstrated the relative all optical PDM processing with discrete devices [8][9][10]. The difficulty for direct PDM signal processing based on the Si devices is mainly due to the polarization sensitivity induced by the nanoscale structure [11]. ...
We propose and fabricate a scheme that combines a two-dimensional (2D) grating coupler and a delay interferometer (DI) in a loop configuration. According to the polarization states, the 2D grating coupler first splits the input signals into two paths, which copropagate in the loop and share a common DI, and then combines the two paths together to the same input port. The proposed device is polarization insensitive and can be used for polarization division multiplexed (PDM) signal processing. For demonstration, the PDM non return-to-zero differential-phase-shift-keying signals can be demodulated successfully. The bit error ratio measurements show an error free operation, reflecting the good performance and the practicability of the proposed device.
This paper designs a 1×2 switchable dual-mode optical 90o hybrid device on the silicon-on-insulator (SOI) platform for the mode division multiplexing hybridized coherent transmission systems in optical communication. Our proposed hybrid uses various 2×2 multimode interference (MMI) couplers, symmetric Y-junctions, and thermo-optic phase shifters. The suggested hybrid device working principle is proved on theoretical analysis about the multimode interference and the transfer matrix relation. The optimization of geometrical parameters and metallic micro-heaters is executed through the numerical simulation method. The proposed hybrid coupler expresses lots of optical performance advantages, with an insertion loss lower than 2.5 dB, a common-mode rejection ratio (CMRR) better than -24 dB, and phase error smaller than 4° in the 50-nm wavelength bandwidth of the third telecom window for both two TE modes. Besides, the device is proven large geometrical tolerances in terms of width and height tolerances larger than ±50 nm and ±6 nm in the 1.5-dB variation limit of transmission, respectively. In addition, the proposed device attains relatively low power consumption under 75 mW and an ultrafast switching time below 10 μs. Such advantages of good performances make the device a promising potential for broadband and intra-chip MDM-hybridized coherent optical communication systems and photonic integrated circuits.
We design an ultracompact, broadband, and low-loss 90-deg optical hybrid coupler using a silicon-on-insulator (SOI) material platform for coherent receivers in optical communication systems. The proposed hybrid coupler uses a cascaded topology that includes five 2 × 2 multimode interference (MMI) couplers in three different fundamental kinds. The working principle of the suggested 90-deg optical hybrid is based on theoretical analysis on the MMI effect and the transfer matrix relations. The optimization of geometrical parameters and the optical characteristics are employing through the numerical simulation method. The investigated 90-deg optical hybrid coupler can be integrated on a microscale footprint as much as 6 μm × 172 μm. Furthermore, our hybrid coupler expresses lots of advantages of optical performances, with an insertion loss lower than 2.6 dB, a common-mode rejection ratio better than −25 dB, and phase error smaller than 5 deg in 90-nm wavelength-bandwidth in the third telecom window. In addition, the designed device, based on the SOI platform, is endowed with large geometrical tolerances possessing width, height, and multimode tolerances corresponding to AE20, AE10, and AE10 nm in the 1-dB variation limit of transmission, respectively. Such advantages of good performances thus make the proposed hybrid device playing the role of a promising potential candidate for widely varying applications of silicon photonics, such as coherent optical receivers, optical interconnects, and high-bitrate optical phase modulators.
Pulse shaping gives communications engineers another degree of freedom in designing a link. It holds promise to allow extending transmission reach, achieve optical multiplexing at highest spectral efficiency or to limit nonlinear distortions. A variety of pulse shapes—rectangular, sinc, raised cosine
to cite just a few—have been investigated but the important question is how optical transmitters can generate such pulses at the necessary speed. Should the transmitter be realized in the digital domain, the all-optical domain or can it be implemented as a hybrid? In this chapter, the fundamentals for pulse shaping in transmitters and receivers are reviewed. A particular emphasis is on orthogonal frequency division multiplexing (OFDM) where the system’s data are encoded onto subcarriers with a rectangularly shaped impulse response, and Nyquist pulse shaping where the symbols are carried by Nyquist pulses. Electronic, digital and optical processors are described and recent experimental demonstrations are reported.
