Cyclic Arrayed Waveguide Grating Research Articles

Monolithically Integrated 8 × 8 Transmitter-Router Based on Tunable V-Cavity Laser Array and Cyclic Arrayed Waveguide Grating Router

A monolithic 8 × 8 transmitter-router chip fabricated on InGaAlAs-InP multi-quantum well wafer for distributed wavelength routing network in the O-band with a channel spacing of 400 GHz is experimentally demonstrated. A tunable V-cavity laser (VCL) array, a cyclic-arrayed waveguide grating router (AWGR) and a semiconductor amplifier (SOA) array are integrated using the quantum-well intermixing (QWI) technique for its fabrication simplicity and cost effectiveness. A 200 GHz-spaced compact-size VCL is demonstrated with a 27 nm tuning range and a side-mode suppression ratio (SMSR) around 40 dB using a single-electrode controlled tuning. The chip output power is 24.6 mW. Measurement results of the transmitter-router chip show that all 64 input-output combinations have cyclic response spectra. After passing through the SOA with 80 mA bias current, an output power of about 9.6 mW and optical signal-to-noise ratio (OSNR) up to 39 dB have been measured. The demonstrated transmitter-router chip is fabricated on the same quantum well structure without requiring multiple epitaxial growth and complex grating fabrication. The characteristics of multi-wavelength and multi-port transmissions enable the distributed optical routing networks with flexible bandwidth allocation, which can find wide application in datacenters and high-performance computers.

Fabrication of Silica Based Silicon 20 Channel Cyclic Arrayed Waveguide Grating

Fabrication of Silica Based Silicon 20 Channel Cyclic Arrayed Waveguide Grating

Monolithic integrated cyclic 64-channel AWG with MZI filters and arrayed vertical reflecting mirrors for WDM-PON application.

The paper introduces a silica-on-silicon monolithic integrated cyclic arrayed waveguide grating (AWG) with Mach-Zehnder interference (MZI) filters and arrayed vertical reflecting mirrors in silicon to realize effective and stable optical transmission between waveguides and photodiodes. The cyclic AWG acts as both multiplexer over the L-band for upstream traffic and demultiplexer over the C-band for downstream traffic. The integrated chip, including AWG, MZI filters, and arrayed reflecting mirrors, has been made successfully with a 6.0 dB insertion loss, which is less than the discrete devices. At the same time, the arrayed reflecting mirrors are more stable than separate reflectors.

提高损耗均匀性的氮氧化硅阵列波导光栅路由器

提高损耗均匀性的氮氧化硅阵列波导光栅路由器

Silicon photonic 8 × 8 cyclic Arrayed Waveguide Grating Router for O-band on-chip communication.

We report an 8 × 8 silicon photonic integrated Arrayed Waveguide Grating Router (AWGR) targeted for WDM routing applications in O-band. The AWGR was designed for cyclic-frequency operation with a channel spacing of 10 nm. The fabricated AWGR exhibits a compact footprint of 700 × 270 μm2. Static device characterization revealed 3.545 dB maximum channel loss non-uniformity with 2.5 dB best-case channel insertion losses and 11 dB channel crosstalk, in good agreement with the simulated results. Successful data routing operation is demonstrated with 25 Gb/s signals for all 8 × 8 AWGR port combinations with a maximum power penalty of 2.45 dB.

Demonstration of flexible multicasting and aggregation functionality for TWDM-PON

The time- and wavelength-division multiplexed passive optical network (TWDM-PON) has been recognized as an attractive solution to provide broadband access for the next-generation networks. In this paper, we propose flexible service multicasting and aggregation functionality for TWDM-PON utilizing multiple-pump four-wave-mixing (FWM) and cyclic arrayed waveguide grating (AWG). With the proposed scheme, multiple TWDM-PON links share a single optical line terminal (OLT), which can greatly reduce the network deployment expense and achieve efficient network resource utilization by load balancing among different optical distribution networks (ODNs). The proposed scheme is compatible with existing TDM-PON infrastructure with fixed-wavelength OLT transmitter, thus smooth service upgrade can be achieved. Utilizing the proposed scheme, we demonstrate a proof-of-concept experiment with 10-Gb/s OOK and 10-Gb/s QPSK orthogonal frequency division multiplexing (OFDM) signal multicasting and aggregating to seven PON links. Compared with back-to-back (BTB) channel, the newly generated multicasting OOK signal and OFDM signal have power penalty of 1.6dB and 2dB at the BER of 10−3, respectively. For the aggregation of multiple channels, no obvious power penalty is observed. What is more, to verify the flexibility of the proposed scheme, we reconfigure the wavelength selective switch (WSS) and adjust the number of pumps to realize flexible multicasting functionality. One to three, one to seven, one to thirteen and one to twenty-one multicasting are achieved without modifying OLT structure.

Large-Scale Optical Switch Utilizing Multistage Cyclic Arrayed-Waveguide Gratings for Intra-Datacenter Interconnection

We develop a design method for creating a large-scale optical switch consisting of two sub-switch parts, i.e., delivery-and-coupling switches and wavelength-routing switches based on cyclic arrayed-waveguide gratings, where the available optical-power budget is optimally allocated to the two sub-switches to maximize the entire switch scale. The power budget necessary for each sub-switch is quantitatively evaluated via extensive computer simulations. The simulation results show that a 1000 × 1000 switch scale can be realized when the available optical-power budget is 23 dB. The simulation results are verified via proof-of-concept experiments.

25 Gbit/s per User Coherent All-Optical OFDM for Tbit/s-Capable PONs

We propose and test a coherent all-optical orthogonal frequency-division multiplexing (AO-OFDM) system, based on all-optical (de)multiplexing and coherent detection, for multiterabit per second (multi-Tbit/s) passive optical networks (PONs). The proposed approach allows us to greatly increase the downstream data rate per user and extend the standard single-mode fiber reach for future long-reach applications. The compliance with a next-generation PON layout is guaranteed thanks to the exploitation of cyclic arrayed waveguide gratings. Five-user transmission with 12.5 Gbaud quadrature phase shift keying modulation per user (125 Gbit/s downstream capacity per wavelength) over a more than 40 km link has been successfully demonstrated.

Integrated Photonic Devices and Applications for 100GbE-and-Beyond Datacom

We review recent progress in integrated photonics devices and their applications for datacom. In addition to current technology used in 100-Gigabit Ethernet (100GbE) with a compact form-factor of the transceiver, the next generation of technology for 400GbE seeks a larger number of wavelengths with a more sophisticated modulation format and higher bit rate per wavelength. For wavelength scalability and functionality, planar lightwave circuits (PLCs), such as arrayed waveguide gratings (AWGs), will be important, as well higher-order-modulation to ramp up the total bit rate per wavelength. We introduce integration technology for a 100GbE optical sub-assembly that has a 4λ x 25-Gb/s non-return-to-zero (NRZ) modulation format. For beyond 100GbE, we also discuss applications of 100GbE sub-assemblies that provide 400-Gb/s throughput with 16λ x 25-Gb/s NRZ and bidirectional 8λ x 50-Gb/s four-level pulse amplitude modulation (PAM4) using PLC cyclic AWGs. key words: integrated photonics, datacom, 100GbE/400GbE, optical subassembly, arrayed waveguide grating

Large-Scale Optical-Switch Prototypes Utilizing Cyclic Arrayed-Waveguide Gratings for Datacenters

We propose novel large-scale optical-switch architectures that utilize delivery and coupling (DC) switches and wavelength routing (WR) switches based on the cyclic arrayed-waveguide gratings (AWGs). To suppress the passband-frequency deviation inherent in cyclic AWGs, we propose two-stage WR structures in which multiple small-scale cyclic AWGs are cascaded to create a large-scale WR switch. We introduce two configurations for constructing a WR switch; the degrees of the first- and second-stage cyclic AWGs are coprime or not. We fabricate both types of optical switches with planar lightwave circuit technologies. A 270 × 270 switch comprised of coprime cyclic AWGs and a 180 × 180 switch comprised of cyclic AWGs whose degrees have a common divisor are compactly fabricated. Transmission experiments confirm their excellent performance.

Low-crosstalk Si arrayed waveguide grating with parabolic tapers.

A silicon arrayed waveguide grating (AWG) with low channel crosstalk was demonstrated by using ultra-short parabolic tapers to connect the AWG's free propagation regions and single-mode waveguides. The tapers satisfied the requirements of low-loss mode conversion and lower channel crosstalk from the coupling of neighboring waveguides in the AWGs. In this work, three different tapers, including parabolic tapers, linear tapers, and exponential tapers, were theoretically analyzed and experimentally investigated for a comparison of their effects when implemented in AWGs. The experimental results showed that the AWG with parabolic tapers had a crosstalk improvement up to 7.1 dB compared with the others. Based on the advantages of parabolic tapers, a 400-GHz 8 × 8 cyclic AWG with 2.4 dB on-chip loss and -17.6~-25.1 dB crosstalk was fabricated using a simple one-step etching process. Its performance was comparable with that of existing AWGs with bi-level tapers, which require complicated two-step etching fabrication processes.

Low-loss wavelength routing optical switch consisting of small matrix switch and cyclic arrayed-waveguide gratings for colorless add/drop

We describe a new wavelength routing switch architecture that uses matrix switches and cyclic arrayed-waveguide gratings (AWGs). By devising connections between them, we construct a large port count optical switch using small port count matrix switches and AWGs. An 80 × 8 switch that consists of 8 × 8 matrix switches and 10 × 1 cyclic AWGs exhibits an insertion loss of only 4–7 dB. This switch enables us to make add/drop ports colorless in the existing reconfigurable optical add/drop multiplexer nodes.

Bidirectional long reach WDM-PON delivering downstream data 20 Gbps and upstream data 10 Gbps using mode locked laser and RSOA

This paper presents long reach wavelength division multiplexing passive optical network (WDM-PON) system capable of delivering downstream 20 Gbit/s data and upstream 10 Gbit/s data on a single wavelength. The optical source for downstream data and upstream data is mode locked laser at central office and reflective semiconductor optical amplifier (RSOA) at each optical network unit. We use two RSOAs at each optical network unit for the 10-Gb/s upstream transmission. The operating wavelengths of these RSOAs are separated by the free-spectral range of the cyclic arrayed waveguide gratings used at the central office and remote node (RN) for (de)multiplexing the WDM channels. We extend the maximum reach of this WDM PON to be 45 km by using Erbium-doped fiber amplifiers at the RN.The hybrid amplifier is designed to enhance the signal power and compensated the fiber dispersion over a wide wavelength range. Optical Equalization technique is used before the receiver to improve modulation bandwidth of an RSOA based colorless optical network unit. Optical Equalization technique helps to improve downlink and uplink performance. Author also investigates analysis of backscattered optical signal for upstream data and downstream data simultaneously. Bit error rate, backscattered optical signal power were measured to demonstrate the proposed scheme. In this paper Long reach and large data service aspects of a WDM-PON is presented.

Configuration of more than N DWDM channels with only one N × N cyclic-AWG-based wavelength routing device

A wavelength routing device based on only one N×N cyclic arrayed waveguide grating (AWG) having easy extended channels configuration is presented in this paper. It is easy to extend the dense wavelength division multiplexing (DWDM) channel configuration through this wavelength routing device. According to the cyclic wavelength of AWG, the wavelength routing devices are easy to configure more than N extended DWDM channels through cascading more proper tunable fiber Bragg gratings (FBGs). With only one 8×8 AWG, two different wavelength routing structures were built to evaluate static crosstalk and the bit-error-rate (BER). Three of the 16 inputted DWDM channels were demonstrated to verify that the proposed wavelength routing device, with only one 8×8 AWG, could configure extended DWDM channels without interfering with other channels. The results show that the wavelength routing device can produces a better performance and offers a cheaper way to extend the DWDM channel configuration for a dynamic network.

Low cost TWDM by wavelength-set division multiplexing

After extensive comparison of candidate technologies, the Full Service Access Network (FSAN) Group in early 2012 made the decision to define Time/ Wavelength Division Multiplexing (TWDM) as the primary solution for the next-generation passive optical network (NG-PON2). A minimum of four wavelengths are foreseen as providing a total capacity per feeder line of 40 Gbit/s downstream and 10 Gbit/s or more upstream. Conventional wavelength division multiplexing (WDM) lasers from core or metro networks are too expensive for fiber to the home (FTTH) systems, because every optical network unit (ONU) will need a tunable laser for upstream transmission. In this paper we will compare different technical solutions and present wavelength-set division multiplexing (WSDM), a scheme developed by Bell Labs as the preferred solution for cost reasons. WSDM uses a laser that can be tuned by an on-chip heater stripe. To exploit this partial wavelength tunability, we do not use contiguous wavelength bands, but wavelength-sets consisting of cyclic interleaved wavelength slots on a fine grid. This wavelength plan can be implemented, e.g., by a cyclic arrayed waveguide grating (AWG) with a small free spectral range. We will describe the concept in detail and report on its experimental validation.

Uplink transmission of a 60-km-reach WDM/OCDM-PON using a spectrum-sliced pulse source

We propose and experimentally demonstrate the uplink transmission of a 60-km-reach wavelength division multiplexing/optical code division multiplexing (WDM/OCDM) passive optical network (PON) using a spectrum-sliced pulse source. As a single light source, a broadband pulse source with a bandwidth of 6.5nm and a repetition rate of 1.25GHz is generated at a central office and supplied to a remote node (RN) through a 50-km fiber link. At the RN, narrow-band pulses (as a source for uplink transmission) are obtained by spectrum slicing the broadband pulse source with a cyclic arrayed waveguide grating and are then supplied to all optical network units (ONUs) via 1×4 power splitters and 10-km drop fibers. Eight wavelengths are obtained with a 6.5-nm bandwidth of the broadband pulse source, and the qualities of the pulses with a repetition rate of 1.25GHz and a pulse width of 45ps for the eight wavelengths are sufficient for four-chip OCDM encoding at the ONUs. In our experiments, four signals are multiplexed by OCDM at one wavelength, and another encoded signal is also multiplexed by WDM. The bit error rates (BERs) of the signals exhibit error-free transmission (BER<10−9) over a 60-km single-mode fiber at 1.25Gb/s.

Implementing Long Reach WDM-PON Delivering Downstream Data 2 Gbps and Upstream Data 70 Gbps on a Single Wavelength using Soliton Pulse

ABSTRACTThis article presents Long Reach Wavelength Division Multiplexing Passive Optical Network (WDM‐PON) system capable of delivering downstream 2 Gbit/s data and upstream 70 Gbit/s data on a single wavelength using pulse source which is mode locked laser that generates a single pulse of “sech” shape with specified power and width. That is, soliton pulse. The optical source for downstream data and upstream data is sech pulse generator at central office (CO) and reflective semiconductor optical amplifier (RSOA) at each optical network unit (ONU). We use two RSOAs at each ONU for the 70‐Gb/s upstream transmission. The operating wavelengths of these RSOAs are separated by the free‐spectral range of the cyclic arrayed waveguide gratings used at the CO and remote node (RN) for (de)multiplexing the WDM channels. We extend the maximum reach of this WDM PON to be 123 km by using Erbium‐doped fiber amplifiers at the RN. The results show that the error‐free transmission can be achieved for all WDM channels in the wavelength range of &gt;35 nm with sufficient power margins. We also investigate analysis of backscattered optical signal for upstream data and downstream data simultaneously. Bit error rate, were measured to demonstrate the proposed scheme. In this article, Long reach and large data service aspects of a WDM‐PON is presented. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2853–2859, 2013

100 Gb/s long‐reach WDM‐PON implemented by using directly modulated RSOA

AbstractThis article presents long reach wavelength division multiplexing passive optical network (WDM‐PON) system capable of delivering 100 Gb/s data to each subscriber. For cost‐effectiveness, WDM‐PON is implemented in loopback configuration using directly modulated reflective semiconductor optical amplifiers (RSOAs) at 25 Gb/s. We use four RSOAs at each optical network unit for the 100‐Gb/s upstream transmission. The operating wavelengths of these RSOAs are separated by the free‐spectral range of the cyclic arrayed waveguide gratings used at the central office and remote node (RN) for (de)multiplexing the WDM channels. We extend the maximum reach of this WDM‐PON to 123 km by using Erbium‐doped fiber amplifiers at the RN. The results show that the error‐free transmission can be achieved for all WDM channels in the wavelength range of &gt;35 nm with sufficient power margins. Bit error rate and Q‐factor were measured to demonstrate the proposed scheme. In this article, long reach and large data service aspects of an access network are presented. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1426–1430, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27581 DOI 10.1002/mop.27572

Large Port Count Wavelength Routing Optical Switch Consisting of Cascaded Small-Size Cyclic Arrayed Waveguide Gratings

We propose a highly scalable switch architecture suitable for client-side cross-connect switches in reconfigurable optical add/drop multiplexers and optical switching in data centers. It consists of cascaded cyclic arrayed waveguide gratings (AWGs). We develop a 270 × 270 prototype switch consisting of an assembly of arrayed small switches and couplers and AWGs that are fabricated on planar lightwave circuit chips. Transmission experiments verify its technical feasibility.

103-Gb/s Long-Reach WDM PON Implemented by Using Directly Modulated RSOAs

We propose and demonstrate a long-reach wavelength-division-multiplexed passive optical network (WDM PON) capable of providing 100-Gb/s service to each subscriber, for the first time to the best of our knowledge. For cost-effectiveness, this network is implemented in loopback configuration by using directly modulated reflective semiconductor optical amplifiers (RSOAs) at 25.78 Gb/s. For the modulation of the RSOA at such a high-speed, we have to minimize the electrical parasitics by using the butterfly package. Also, to overcome the limited bandwidth of the RSOA, we utilize the electronic equalization technique at the receiver. We use four RSOAs at each optical network unit for the 103-Gb/s upstream transmission. The operating wavelengths of these RSOAs are separated by the free-spectral range of the cyclic arrayed waveguide gratings used at the central office and remote node (RN) for (de)multiplexing the WDM channels. We extend the maximum reach of this WDM PON to be >; 120 km by using Erbium-doped fiber amplifiers at the RN. The results show that the error-free transmission can be achieved for all WDM channels in the wavelength range of >; 35 nm with sufficient power margins.