16-channel Arrayed Waveguide Grating Research Articles

Silicon Nanowire-Assisted High Uniform Arrayed Waveguide Grating

Determining how to improve the non-uniformity of arrayed waveguide grating (AWG) is of great significance for dense wavelength division multiplexing (DWDM) systems. In this work, a silicon nanowire-assisted AWG structure is proposed, which can achieve high uniformity with a low insertion loss. The article compares the effect of nanowire number and shape on uniformity and insertion loss, finding that double nanowires provide the best performance. Double nanowires with a width of 230 nm and length of 3.5 μm can consist of a slot configuration between arrayed waveguides, both connecting to the star coupler and spacing 165 nm from the waveguides. Compared with conventional 8- and 16-channel AWGs with channel spacing of 200 GHz, the non-uniformity of the presented structure can be improved from 1.09 and 1.6 dB to 0.24 and 0.63 dB, respectively. The overall footprint of the device would remain identical, which is 276 × 299 or 258 × 303 μm2 for the 8- or 16-channel AWG. The present high uniformity design is simple and easy to fabricate without any additional insertion loss, which is expected to be widely applied in the highly integrated DWDM systems.

Hybrid-Integrated Comb Source With 16 Wavelengths

Comb sources and multi-wavelength lasers can be used as central sources of light in many communication systems using high channel count wavelength division multiplexing. Here, we demonstrate a 16 wavelengths comb source built through large scale hybrid integration of 16 active gain chips with a passive silica chip that incorporates a 16 channel arrayed waveguide grating. Optical coupling between the 16 gain chips and the silica chip is achieved through 32 ball lenses (two per channel), that are aligned and attached in place with an automated process that we developed. The 16 channels have 100 GHz spacing and are centered in the C-band. We show monomode lasing, both in single-channel and multi-channel operation, with side mode suppression ratio as high as, respectively, 67 dB and 55 dB. The total output power of our comb source is about 17.9 dBm when all the 16 channels are activated simultaneously. The channels of our multi-wavelength laser have very narrow Lorentzian linewidths, with best value as narrow as 880 Hz and worst value of about 3.6 kHz. Our comb source integrates hybridly a large number of optical components, however thanks to the parallel architecture and the possibility of packaging the lenses with an automated process, our integration approach can be scaled to an even higher number of channels.

Eight-wavelength receiver optical subassembly based on silica hybrid integrated technology

A receiver optical subassembly (ROSA) based on hybrid integrated technology is designed and fabricated. It consists of an 8-channel arrayed waveguide grating (AWG) with 2% refractive index difference, two 4-channel positive intrinsic-negative photodetector arrays, and two 4-channel transimpedance amplifier arrays. A flat-top optical spectrum was observed because the output waveguides have a multimode structure, and the average 1-dB bandwidth of AWG channels is 2.8 nm. The insertion loss of all channels is between −1.8 and −2.9 dB, and the cross talk between adjacent channel is less than −20 dB. The ROSA shows a maximum responsivity of 0.4 A / W and 3-dB bandwidth of more than 22 GHz for four channels, which can meet the data transmission rate of 25 Gb / s. In the future, we will improve the fabrication process to achieve a transmission rate of 8 × 25 Gb / s.

Integrated Silicon-on-Insulator Spectrometer With Single Pixel Readout for Mid-Infrared Spectroscopy

Mid-infrared spectroscopy in the 2–4 $\mu$ m wavelength range is of cardinal value for many sensing applications. Current solutions involve bulky and expensive systems to operate. Silicon-on-Insulator (SOI) waveguide technology offers means to miniaturize the different parts of the spectrometer. However, the development of on-chip detectors for the mid-infrared wavelength range is in its infancy and the characteristics are not on par with their discrete (cooled) counterparts. In this work, a compact and cheap mid-infrared spectrometer is realized by integrating a SOI arrayed waveguide grating (AWG) spectrometer operating in the 2.3 $\mu$ m wavelength range with a high performance mid-infrared photodiode. The AWG has 12 output channels with a spacing of 225 GHz (4 nm) and a free spectral range of 3150 GHz (56 nm), which are simultaneously collected by a single, transistor outline (TO)-packaged extended InGaAs PIN photodiode. The response of each AWG channel is discerned by time-sequentially modulating the optical power in each output channel using integrated Mach-Zehnder based thermo-optic modulators with a $\pi$ -phase shift power consumption of $\approx$ 50 mW. As an example, the absorption spectrum of a 0.5 mm thick polydimethylsiloxane sheet is sampled and compared to a benchtop spectrometer to good agreement.

Interferometric imaging using Si3N4 photonic integrated circuits for a SPIDER imager.

This paper reports design, fabrication, and experimental demonstration of a silicon nitride photonic integrated circuit (PIC). The PIC is capable of conducting one-dimensional interferometric imaging with twelve baselines near λ = 1100-1600 nm. The PIC consists of twelve waveguide pairs, each leading to a multi-mode interferometer (MMI) that forms broadband interference fringes or each corresponding pair of the waveguides. Then an 18 channel arrayed waveguide grating (AWG) separates the combined signal into 18 signals of different wavelengths. A total of 103 sets of fringes are collected by the detector array at the output of the PIC. We keep the optical path difference (OPD) of each interferometer baseline to within 1 µm to maximize the visibility of the interference measurement. We also constructed a testbed to utilize the PIC for two-dimension complex visibility measurement with various targets. The experiment shows reconstructed images in good agreement with theoretical predictions.

Tunable wavelength generation in the 1 µm region incorporating a 16-channel arrayed waveguide grating (AWG)

A tunable single- and dual-wavelength ytterbium-doped fiber laser, incorporating a 16-channel arrayed waveguide grating is proposed and demonstrated. The side mode suppression ratio from the proposed setup has an average value of 52.97 dB (single-wavelength generation) and 58.19 dB (dual-wavelength generation). The tunable dual wavelength ranged from 1039.98 nm to 1047.48 nm with wavelength spacing ranging from 0.50 nm to 7.5 nm. A stability test from the experiment shows a power variation of 0.8 dB, and a wavelength fluctuation of 0.02 nm indicates the stability and reliability of the proposed work.

Time- and Wavelength-Multiplexed Wavelength Shift Detection for High-Resolution, Low-Cost Distributed Fiber-Optic Sensing

We present a concept for time- and wavelength-multiplexed readout of wavelength-encoded fiber optic sensors, useful for low-cost distributed sensing and high-resolution monitoring in critical applications such as battery management and energy systems. By taking advantage of the unused photodetector bandwidth in a wavelength-multiplexed fiber Bragg grating (FBG) sensing system based on an arrayed waveguide grating (AWG), we can time-multiplex the detection of 100s of FBG sensors. Our initial implementation is capable of monitoring over 100 sensors at a simultaneous readout rate of 100 Hz with sensor crosstalk below 100 fm and wavelength noise of 11.5 fm Hz–1/2 from 10 to 50 Hz; the light source used to illuminate the FBGs is the dominant contributor to this noise. We present a simplified theoretical framework for understanding system tradeoffs in terms of AWG channel spacing and a sensor slope factor.

Experimental Demonstration of Birefringence Compensation Using Angled Star Couplers in Silica-Based Arrayed Waveguide Grating

A birefringence compensation technique based on angled star couplers in arrayed waveguide grating (AWG) is experimentally investigated in silica-on-silicon waveguide with B–Ge codoped upper cladding. A 16-channel AWG with 100-GHz channel spacing is designed and fabricated. The star couplers are designed according to Rowland circle construction with an oblique incident/diffraction angle. Five different polarization compensation parameters corresponding to different incident/diffraction angles are employed to investigate the stress-induced birefringence. The experimental results confirm that the polarization-dependent wavelength shift <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX"> $(\hbox{PD}\lambda)$</tex></formula> can be tuned by varying the incident/diffraction angle at the star couplers, and a birefringence-free AWG can be achieved without any additional fabrication process.

Low‐resolution Raman spectroscopy over a wide spectral range with a single‐diffraction order arrayed‐waveguide grating

An integrated arrayed‐waveguide grating (AWG) fabricated in silicon oxynitride (SiON) technology is used as the wavelength separation and selection element for Raman spectroscopy. With a spectral resolution of 5.5 nm and a free spectral range of 215 nm, the AWG enables wavelength separation of the full Raman fingerprint region in a single diffraction order without order overlap. It is demonstrated that Raman signal detection of cyclohexane with the AWG is feasible and that the information on position and relative intensities of the Raman bands of cyclohexane are preserved. A detailed description of the signal processing methodology to obtain AWG‐based Raman measurements corrected for instrument response is presented. The Raman measurement based on the integrated intensity output of the device corresponds well to the expected relative intensity channel output of the AWG. Raman information based on band intensity ratios from the AWG channels is also preserved compared with the spectral integration of bands, with a maximum relative error of 9% attributed to some light that might have leaked from the channels to the device substrate. These results are a step towards the realization of a technology suitable for dedicated, low‐cost, miniaturized Raman devices. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Wide-band fanned-out supercontinuum source covering O-, E-, S-, C-, L- and U-bands

A wide-band supercontinuum source generated by mode-locked pulses injected into a Highly Non-Linear Fiber (HNLF) is proposed and demonstrated. A 49cm long Bismuth–Erbium Doped Fiber (Bi–EDF) pumped by two 1480nm laser diodes acts as the active gain medium for a ring fiber laser, from which mode-locked pulses are obtained using the Non-Polarization Rotation (NPR) technique. The mode-locked pulses are then injected into a 100m long HLNF with a dispersion of 0.15ps/nmkm at 1550nm to generate a supercontinuum spectrum spanning from 1340nm to more than 1680nm with a pulse width of 0.08ps and an average power of −17dBm. The supercontinuum spectrum is sliced using a 24 channel Arrayed Waveguide Grating (AWG) with a channel spacing of 100GHz to obtain a fanned-out laser output covering the O-, E-, S-, C-, L- and U-bands. The lasing wavelengths obtained have an average pulse width of 9ps with only minor fluctuations and a mode-locked repetition rate of 40MHz, and is sufficiently stable to be used in a variety of sensing and communication applications, most notably as cost-effective sources for Fiber-to-the-Home (FTTH) networks.

650 nm聚合物阵列波导光栅波分复用器设计

By choosing Polymethyl Methacrylate-glycidyl Methacrylate[P(MMA-GMA)] with a low absorption loss at 650 nm as the cladding material of a waveguide,and taking the bisphenol A epoxy resin as the refractive index modifier,the cross section size of a single mode waveguide was designed according to the refractive index of the cladding and core material.Then the layout of a 16-channel Arrayed Waveguide Grating(AWG) was designed and optimized using beam propagation method.The Optiwave software was used to simulate the optical propagation characteristics of the AWG,and results show that the channel spacing is 0.845 01 nm,the device insertion loss is less than 14 dB,and the crosstalk is less than-25 dB.

Wavelength Interrogator Based on Closed-Loop Piezo-Electrically Scanned Space-to-Wavelength Mapping of an Arrayed Waveguide Grating

We demonstrate a novel technique for the interrogation of grating-based fiber optic sensors. The proposed technique is based on space-to-wavelength mapping using an arrayed waveguide grating (AWG). The beam position along the AWG input coupler is controlled by a closed-loop piezoelectric motor. By employing a real-time position feedback encoder, the absolute position of the input light beam can be accurately obtained, which would yield a precise interrogation of the wavelength due to a fixed relationship between the beam position and the transmission wavelength of the AWG channel. The proposed system for the interrogation of fiber Bragg grating (FBG) sensors and a tilted-FBG sensor is experimented. An interrogation resolution of 3 pm and an interrogation range of 18 nm are demonstrated as well as the multichannel measurement capability. Initial results show that the proposed interrogation system has the potential of being packaged into a compact, light weight, and cost-effective interrogator with good performance.

Investigation of all-optical analog-to-digital quantization using a chalcogenide waveguide: A step towards on-chip analog-to-digital conversion

We have investigated all-optical analog-to-digital quantization by broadening the pulse spectrum in a chalcogenide (As 2S 3) waveguide and subsequently slicing the measured spectrum using an array of filters. Pulse spectral broadening was measured for 8 different power levels in a 6 cm long As 2S 3 waveguide and used to analyze an 8-level all-optical quantization scheme employing filters with full-width at half-maximum (FWHM) bandwidth of 2 nm. A supercontinuum spectrum with −15 dB spectral width up to 324 nm was observed experimentally at large powers. This large spectral broadening, combined with filtering using a 128 channel arrayed waveguide grating (AWG) with 2 nm filter spacing, has the potential for all-optical quantization with 7-bit resolution. In order to encode the quantized signal we propose an encoder scheme which can be implemented using optical Exclusive-OR gates. Demonstrating all-optical quantization using a planar waveguide is an important step towards realizing all-optical A/D conversion on a chip.

Tunable dual wavelength fiber laser incorporating AWG and optical channel selector by controlling the cavity loss

In this paper, we propose and demonstrated a dual wavelength fiber laser (DWFL) based on the use of an erbium doped fiber (EDF) gain medium as well as an 1 × 24 Arrayed Waveguide Grating (AWG) together with two optical channel selectors (OCS) to provide channel spacing tunability. The output power of the two wavelengths is equalized by controlling the cavity loss in the DWFL using two Programmable Optical Attenuators (POAs). The widest spacing obtained from the DWFL is 18.13 nm while the narrowest spacing is 0.8 nm. The DWFL has good stability with only minor power fluctuations of less than 1.5 dB and a Side Mode Suppression Ratio (SMSR) of approximately 69.1 dB with peak fluctuations of less than 2.3 dB.

Monolithic AWG-based Discretely Tunable Laser Diode With Nanosecond Switching Speed

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A novel concept for an arrayed-waveguide-grating (AWG)-based fast tunable laser is presented. It is fabricated in the InP–InGaAsP monolithic integration technology. Laser peaks have a sidemode suppression ratio of 30–40 dB. The wavelength switching speed is in the order of a few nanoseconds and switching is achieved by a 1-mA bias current. The switching between AWG channels is discrete and no laser operation takes place at wavelengths corresponding to other channels during the tuning process. </para>

Modeling of arrayed waveguide grating for wavelength interrogation application

We have proposed and discussed a design of arrayed waveguide grating (AWG) for the application of wavelength interrogation. The spectral responses of a silica-based 16 channel AWG with channel spacing 1.6nm have been simulated when different receiver waveguide spacing are used. It was found that the 3-dB bandwidth is reduced about 50% as the receiver waveguide spacing increasing from 20μm to 30μm. The effect of bandwidth of the spectral response on wavelength resolution of AWG based interrogator has been estimated and discussed.

1.5%-/spl Delta/ athermal arrayed-waveguide grating multi/demultiplexer with very low loss groove design

We describe a compact 1.5%-/spl Delta/ athermal silica-based 100-GHz-spacing 16-channel arrayed-waveguide grating (AWG) multi/demultiplexer with a modified groove design for a very low excess loss. We propose new approaches for modifying the shape of the grooves and the arrayed waveguides and optimize the shape modifications for 1.5%-/spl Delta/ waveguides. By employing this modified groove design, we greatly reduced the groove excess loss from 1.9 to 0.4 dB in the 1.5%-/spl Delta/ athermal AWG.

Interrogation of fibre Bragg grating sensors using an arrayed waveguide grating

We experimentally investigate the use of an arrayed waveguide grating (AWG) to interrogate fibre Bragg grating (FBG) sensors. A broadband light source is used to illuminate the FBG sensors. Reflected spectral information is directed to the AWG containing integral photodetectors providing 40 electrical outputs. Three methods are described to interrogate FBG sensors. The first technique makes use of the wavelength-dependent transmission profile of an AWG channel passband, giving a usable range of 500 με and a dynamic strain resolution of 96 nε Hz−1/2 at 13 Hz. The second approach utilizes wide gratings larger than the channel spacing of the AWG; by monitoring the intensity present in several neighbouring AWG channels an improved range of 1890 με was achieved. The third method improves the dynamic range by utilizing a heterodyne approach based on interferometric wavelength shift detection, providing an improved dynamic strain resolution of 17 nε Hz−1/2 at 30 Hz.

Design and fabrication of a broadband polarization and temperature insensitive arrayed waveguide grating on InP

An arrayed waveguide grating (AWG) with a novel S-shaped design for broadband operation is demonstrated for the first time with III-V semiconductors. This device design provided a polarization and temperature insensitive operation. It is also shown that, despite the wide operating range, chromatic dispersion does not degrade the performance of the AWG. The AWG is operational above the absorption edge of the semiconductor (1100nm) and can function for a wide range of wavelengths covering the coarse wavelength multiplexing range from 1270nm to 1610nm. A four channel AWG with this novel design was fabricated and characterized.

Performance Analysis of the Fiber Bragg Grating Interrogation System Based on an Arrayed Waveguide Grating

In this paper, we analyze the performance of the fiber Bragg grating (FBG) interrogation system based on an arrayed waveguide grating (AWG) device. The spectrum of light reflected from the FBG sensor is analyzed using an AWG, which acts as a coarse spectrometer. Using measurement points from the AWG channels, the original spectrum of the sensing element is reconstructed by means of curve fitting. The measurement system is modeled in the LabView environment, which allows the modification of the FBG and AWG parameters and simulating the measurement process. This, in turn, allows the quantification of the measurement errors resulting from the nonlinearity of the particular FBG/AWG configuration, and allows the optimization of the system design for the particular measurement errors permitted. In addition to the simulations of the proposed measurement system, we provide details of the laboratory evaluation.