Four-channel Wavelength Division Multiplexing Research Articles

Chip-encoded high-security classical optical key distribution

Abstract The information security plays a significant role in both our daily life and national security. As the traditional algorithm-based secure key distribution (SKD) is challenged by the quantum computers, the optical physical-layer SKD has attracted great attentions such as quantum SKD, chaos SKD, and reciprocity-based SKD. However, the cost of quantum SKD is still unaffordable and the latter two classical SKDs are only reliable with some preshared information or under simple eavesdrop. So far, there still lacks a high-security and low-cost optical SKD scheme. In this paper, we propose and demonstrate a high-security chip-encoded classical optical SKD paradigm based on the reciprocity of incoherent matrix. The security of SKD is facilitated by the incoherence of input light, and it is the first time that the classical optical SKD is achieved with silicon photonic chips and commercial optical fiber link. Experimentally, we set up a chip-to-chip communication link and achieve key generation rate of 100 bit/s over a 40 km single mode fiber, with key error rate of only 1.89 %. Moreover, we demonstrate the key capacity expansion of the proposed scheme with four-channel wavelength division multiplexing. Our proposal paves the way for the low-cost, high-security, and miniaturized optical SKD.

Compact MMI-Based AWGs in a Scalable Monolithic Silicon Photonics Platform

We demonstrate a compact ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$367 \times 67 \, \mu {\text{m}}^2$</tex-math></inline-formula> ) four-channel wavelength division multiplexer using an arrayed waveguide grating based on multimode interference couplers, and built on a monolithic silicon photonics platform. The design is particularly attractive due to the thin device layer. A semi-numerical approach was used for device design and simulation. Optical measurements were found to be consistent with simulation results. The device channel spacing, 3-dB bandwidth and crosstalk were measured to be 97 GHz, 87 GHz and 9.6 dB, respectively, for the designed wavelength of operation near 1310 nm.

Bidirectional grating based interleaved angled MMI for high-uniformity wavelength division (de)multiplexing and surface-normal fiber packaging.

We propose and experimentally demonstrate a vertical fiber interfacing interleaved angled multimode interference (MMI) coupler for wavelength-division multiplexing (WDM) applications. This four-channel WDM device comprises two 1×2 angled MMI couplers and a bidirectional grating-based Mach-Zehnder interferometer (MZI) structure. In the MZI optical interleaver, the uniform bidirectional grating functions as both the perfectly vertical grating coupler and the 3 dB power splitter. Benefitting from the flat-top coupling spectrum of the grating coupler, a high-uniformity wavelength-division (de)multiplexing can be achieved with a simulated insertion loss of 3.15-3.36 dB (the nonuniformity of 0.22 dB). The angled MMIs (AMMIs) are designed and optimized using the eigenmode expansion method. For wavelength matching between the MZI and AMMIs, the circuit simulation model of the interleaved AMMI is built by importing the S-parameter matrices of all the optical components extracted from the physical level simulations. The device was fabricated using standard CMOS technology and all the features were patterned with the 193-nm deep-UV lithography. Experimental results obtained without thermal tuning are in good agreement with the simulation results. The device exhibits an insertion loss of 4.5-4.65 dB (nonuniformity of 0.15 dB), channel spacing of 10 nm, and cross talk of -(21.62-26)dB.

Receiver Integration with Arrayed Waveguide Gratings toward Multi-Wavelength Data-Centric Communications and Computing

This paper reviews receivers that feature low-loss multimode-output arrayed waveguide gratings (MM-AWGs) for wavelength division multiplexing (WDM) as well as hybrid integration techniques with high-speed throughput of up to 100 Gb/s and beyond. A design of optical coupling between higher-order multimode beams and a photodiode for a flat-top spectral shape is described in detail. The WDM photoreceivers were fabricated with different approaches. A 10-Gb/s photoreceiver was developed for a 1.25-Gb/s baud rate and assembled for eight-channel WDM by mechanical alignment. A receiver with 40-Gb/s throughput was built by using visual alignment for a 10-Gb/s baud rate and four-channel WDM. A 100-Gb/s receiver assembled by active alignment with a four-channel by 25-Gb/s baud rate is the basis for beyond-100 Gb/s and future multi-wavelength integrated devices toward data-centric communications and computing.

O-Band Silicon Photonic Transmitters for Datacom and Computercom Interconnects

Today, the datacenter ecosystems are fueling the demand for novel transmitter (ΤΧ) technologies complying with the off-board, on-board, and chip-to-chip computing needs. This has set a new class of requirements for the TX infrastructure that should now offer multiple credentials, namely: high-speed, O-band operation for avoiding dispersion compensation in long distances, wavelength-division multiplexing (WDM) capabilities for higher throughput and multicasting/broadcasting support, and tight co-packaging with low-power electronics. Silicon (Si) photonic TXs have been extensively studied toward high-speed and WDM TX engines targeting mainly C-band. Only a limited number of Si-Pho O-band TXs have been reported, however with ≤32 Gb/s/channel line-rate capabilities and with a WDM portfolio that has not been fully explored yet. In this paper, we introduce a novel silicon photonic high-speed O-band TX hardware platform that can meet the current datacom and computercom interconnect requirements. We demonstrate a ring modulator (RM) based four-channel WDM TX at 4 × 40 Gb/s non-return-to-zero (NRZ) operation that supports wavelength parallelism in unicast operation but can also pave the way toward WDM TX engines for the post-100 GbE TX era. Moreover, we present a broadband Si Mach–Zehnder modulator employed in a WDM modulation scheme of 2 × 25 Gb/s NRZ signals and demonstrate multicasting when combined with a 8 × 8 passive arrayed waveguide grating router (AWGR) wavelength router, addressing the broadcasting needs of traffic usually encountered in cache-coherent multisocket settings. Finally, we further demonstrate the tight synergy of O-band Si-RM modulators with high-speed CMOS electronics, presenting an RM-based TX assembly prototype employing a fully depleted silicon-on-insulator CMOS driver, delivering 50-Gb/s NRZ operation.

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Comparison of the Optical Amplifiers EDFA and SOA Based on the BER and Q-Factor in C-Band

Currently it is not possible to create a fully optical communication system without a software tool which simulates an optical communication line in real conditions prior to its construction. The aim of this article is to establish a comparison between the EDFA (erbium doped fibre amplifier) and SOA (semiconductor optical amplifier) optical amplifiers in the WDM (wavelength division multiplexing) system. The system contains a four-channel WDM with speed of 10 Gbps and optical fibre with length of 80 km. Simulations are conducted in the programme environment “OptSim.” The quality of the optical communication system is evaluated by the BER (bit error rate) and Q-factor for individual wavelengths, namely, of 1558 nm and 1562 nm, which are within the C-band.

Bidirectional optical subassembly-shaped 20 - Gbit / s compact single-mode four-channel wavelength-division multiplexing optical modules for optical multimedia interfaces

Low-cost single-mode four-channel optical transmitter and receiver modules using the wavelength-division multiplexing (WDM) method have been developed for long-reach fiber optic applications. The single-mode four-channel WDM optical transmitter and receiver modules consist of two dual-wavelength optical transmitter and receiver submodules, respectively. The integration of two channels in a glass-sealed transistor outline-can package is an effective way to reduce cost and size and to extend the number of channels. The clear eye diagrams with more than about 6 dB of the extinction ratio and the minimum receiver sensitivity of lower than −16 dBm at a bit error rate of 10−12 have been obtained for the transmitter and receiver modules, respectively, at 5 Gbps/channel. The 4K ultrahigh definition contents have been transmitted over a 1-km-long single-mode fiber using a pair of proposed four-channel transmitter optical subassembly and receiver optical subassembly.

Four-Channel WDM Transmission Over 50-m SI-POF at 14.77 Gb/s Using DMT Modulation

Wavelength division multiplexing (WDM) is a promising solution for upgrading the capacity of polymer optical fiber (POF)-based telecommunication networks. In this letter, we report on the successful realization of a four-channel high-speed WDM transmission system for 1-mm diameter step-index POF (SI-POF). For combining the optical signals coming from 405-, 450-, 515-, and 639-nm laser diodes onto 1-mm SI-POF, a \(4 \times 1\) coupler with low insertion loss (IL) has been developed. To spatially separate different wavelength channels, a four-channel demultiplexer with low IL ( 30 dB) has been realized in bulk optics. The 14.77-Gb/s data transmission based on the offline-processed discrete multitone modulation technique has been demonstrated over 50-m SI-POF at a bit-error rate of \(10^{{{-3}}}\) .

Fabrication-Tolerant Four-Channel Wavelength-Division-Multiplexing Filter Based on Collectively Tuned Si Microrings

We demonstrate a robust, compact and low-loss four-channel wavelength-division multiplexing (WDM) filter based on cascaded double-ring resonators (2RR) in silicon. The flat-top channel response obtained by the second-order filter design is exploited to compensate for the detrimental effects of local fabrication variations and their associated phase errors on the ring-based filter response. Full wafer-scale characterization of a cascaded, four-channel 2RR filter with channel spacing of 300 GHz shows an average worst-case insertion loss below 1.5 dB and an average worst-case crosstalk below -18 dB across the wafer, representing a substantial improvement over a first-order based ring (1RR) design. The robust 2RR filter design enables the use of a simple collective thermal tuning mechanism to compensate for global fabrication variations as well as for global temperature fluctuations of the WDM filter, the WDM laser source, or both. Highly uniform collective heating is demonstrated using integrated doped silicon heaters. The compact filter footprint of less than 50×50 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> per channel enables straightforward scaling of the WDM channel count to 8 channels and beyond. Such low-loss collectively tuned ring-based WDM filters can prove beneficial in scaling the bandwidth density of chip-level silicon optical interconnects.

Filter-embedded four-channel WDM module fabricated from fluorinated polyimide

Filter-embedded four-channel wavelength-division multiplexers for wavelength-division multiplexing (WDM) systems are fabricated from polyimide waveguides. The WDM module has a wide passband of over 30 nm, low insertion loss, and low crosstalk. The insertion loss and crosstalk for each port were less than 4.9 dB and better than -20 dB, respectively. The reliability of the WDM was examined, and it passed the change of temperature and damp heat tests of the International Electrotechnical Commission (IEC) category C.

Four-channel coarse WDM for inter- and intra-satellite optical communications

A polymer volume grating-based four-channel coarse wavelength division multiplexer (WDM) for inter- and intra-satellite optical communication application is reported for the first time. This compact four-channel WDM device working at 0.83, 1.06, 1.34 and 1.55 μm is designed to build a complete optical link between two satellites, where wavelengths of 0.83 and 1.55 μm are used for data stream channels, 1.06 and 1.34 μm are used for inter- and intra-satellite connection. It is for the first time reported that a WDM device can cover such a large wavelength range in a single substrate. For transverse electric (TE) wave, the channel efficiencies at 0.83, 1.06, 1.34 and 1.55 μm are 55%, 40%, 35% and 45%, respectively. Channel efficiencies for transverse magnetic (TM) waves are 20% lower than those of TE waves on average. Wavelength shifts due to Doppler effect, temperature variations and radiation effects in space can be adequately accommodated.

Superimposed grating wavelength division multiplexing in Ge-doped &lt;inline-formula&gt;&lt;roman&gt;SiO&lt;/roman&gt;&lt;sub&gt;&lt;roman&gt;2&lt;/roman&gt;&lt;/sub&gt;&lt;roman&gt;/Si&lt;/roman&gt;&lt;/inline-formula&gt; planar waveguides

An improved model of wavelength division multiplexing (WDM) by superimposed gratings in planar waveguides has been developed. Based on this theory, principal design rules of N-channel WDM are established and a fanout capacity of 100 is estimated. Finally, fourchannel WDM at 840 nm has been demonstrated on a Ge:SiO2 /SiO2 /Si planar waveguide, which was hydrogenated to enhance its photosensitivity. The superimposed gratings were written using a narrow linewidth KrF excimer laser in an interferometric setup used in inscribing fiber Bragg gratings.

Silicon-on-insulator (SOI) phased-array wavelength multi/demultiplexer with extremely low-polarization sensitivity

We demonstrate the first phased-array wavelength multiplexer fabricated in the silicon-on-insulator (SOI) waveguide technology. The four-channel wavelength division multiplexer (WDM) has a channel spacing of 1.9 nm centered at 1550-nm wavelength and a 3-dB channel bandwidth of 0.72 nm. The crosstalk to neighboring channels is less than -22 dB and the on-chip insertion loss is below 6 dB for all channels. The TE-TM shift is less than 0.04 nm which is the smallest attained without compensation techniques in any integrated optic technology.

Learning method for neural networks using weight perturbation of orthogonal bit sequence and its application to adaptive WDM demultiplexer

This paper proposes a novel on-chip learning method for hardware-implemented neural networks to achieve an adaptive wavelength division multiplexer (WDM) demultiplexer. The parameters of the neural network are perturbed by orthogonal bit sequences with small amplitude. The parameters are corrected based on the correlation detection result between the perturbed error signal and the corresponding perturbation signal. A learning experiment that transmits 200-Mb/s, four-channel WDM signals through a 40-km fiber and the tracking of the wavelength drift of the optical transmitter successfully demonstrate the proposed method.

Cascade self-induced holography: a new grating fabrication technology for DFB/DBR lasers and WDM laser arrays

A method of fabricating submicron gratings for optoelectronic devices from a glass mask was proposed and demonstrated. The glass mask has gratings on both sides with a period of at least four times the final feature size. By introducing an offset to the grating periods on the mask, one can achieve multiple-period gratings with a very fine period spacing for advanced wavelength-division multiplexing (WDM) devices. In this paper, we demonstrated 0.5-/spl mu/m second-order gratings for 1.55-/spl mu/m DFB lasers and gratings with a 6-/spl Aring/ period difference for a four-channel WDM laser array using only optical sources. The Moire pattern caused by the spatial frequency beating was also observed and discussed. The Moire pattern could serve as an effective tool to measuring wavelength channel spacing between devices with an unprecedented (0.1 /spl Aring/) resolution.

10-Gb/s, 4-channel wavelength division multiplexing fiber transmission using semiconductor optical amplifier modules

A dense wavelength-division-multiplexing (WDM) transmission system with very-high-speed channels was investigated experimentally. A 10-Gb/s four-channel WDM optical transmission (total capacity of 40 Gb/s) over a 40-km dispersion-shifted fiber was achieved by using hybrid-integrated DFB-LD/driver modules for transmitters and two cascaded semiconductor optical amplifier (SOA) modules for receivers. The experiment confirmed that the SOA is applicable for WDM transmission systems with high bit rates because of its inherent wide bandwidth. The transmission capacity of 40 Gb/s, achieved using an intensity modulation/direct detection (IM/DD) scheme, is the highest ever reported. This technology will make possible ultralarge capacity (up to several-hundred gigabits per second) and long-haul transmission systems in the future. >

Four-channel wavelength division multiplexer on Ti:LiNbO 3

A tunable Ti:LiNbO 3 four-channel wavelength division multiplexer is demonstrated. Three sections of the TMI (two-mode interference) structure cascaded in two stages are integrated into this device. The operation wavelength is between 750 and 840 nm. Measured adjacent channel crosstalk ranges from −18 to −33 dB

Loss analysis of laser-fiber coupling and fiber combiner, and its application to wavelength division multiplexing: errata

The combination of index-guided laser diodes and wavelength-independent multiplexers is shown to be the best choice for wavelength-division-multiplexing (WDM) systems. Such a transmitter end of a four-channel WDM system will only cause an insertion loss of 1.5 dB or less (laser-fiber coupling plus multiplexer), which is hard to obtain with wavelength-selective multiplexing. In the case of gain-guided lasers it will depend on the number of channels and wavelength separation whether or not wavelength-independent multiplexing is preferable. To include all types of laser diode we had to extend laser-fiber coupling theory to astigmatic laser diodes. The surprisingly simple exact relations based on Gaussian beam analysis show that the usual gain-guided lasers (astigmatism of ~20 μm) are not able with symmetric lenses to launch more than ~20% of their power into a single-mode fiber, whereas an index-guided laser with the same far-field divergence couples ~85%.

Loss analysis of laser-fiber coupling and fiber combiner, and its application to wavelength division multiplexing

The combination of index-guided laser diodes and wavelength-independent multiplexers is shown to be the best choice for wavelength-division-multiplexing (WDM) systems. Such a transmitter end of a four-channel WDM system will only cause an insertion loss of 1.5 dB or less (laser-fiber coupling plus multiplexer), which is hard to obtain with wavelength-selective multiplexing. In the case of gain-guided lasers it will depend on the number of channels and wavelength separation whether or not wavelength-independent multiplexing is preferable. To include all types of laser diode we had to extend laser-fiber coupling theory to astigmatic laser diodes. The surprisingly simple exact relations based on Gaussian beam analysis show that the usual gain-guided lasers (astigmatism of ~20 microm) are not able with symmetric lenses to launch more than ~20% of their power into a single-mode fiber, whereas an index-guided laser with the same far-field divergence couples ~85%.