Proposal for loadable and erasable optical memory unit based on dual active microring optical integrators

A novel approach for loadable and erasable optical memory unit based on dual microring optical integrators is proposed and studied. The optical integrator, which can generate an optical step function for data storing, is synthesized using active media for loss compensation and a tunable phase shifter for data reading at any time. The input data into the memory is return-to-zero (RZ) signal, and the output data read from the memory is also RZ format with a narrower pulse width. An optical digital register based on the proposed optical memory unit is also investigated and simulated, which shows the potential for large scale data storage and serial-to-parallel data conversion. A great number of such memory units can be densely integrated on a photonic circuit for future large scale data storage and buffer.     

CCD探测器在可擦除光存储实验中的应用

本文利用ＣＣＤ作为光探测器采集和测量可擦除光存储实验中连续变化的衍射信号,对用ＣＣＤ进行实时动态信号的测量原理和特点做了探讨,并设计了一套ＣＣＤ探测装置用于采集、显示和分析甲基红偶氮染料掺杂的聚乙烯醇（ＭＲ／ＰＶＡ）和酸化甲基红偶氮染料掺杂的聚乙烯醇（ＡＭＲ／ＰＶＡ）薄膜材料的光存储数据该装置操作简单,结果直观,具有较高的测量速度和测量精度,适于动态光信号测量。     

Improved optical packet switching structure with recirculation buffer and feedback tunable wavelength converter

The performance of an optical switching network is mainly determined by its core node structure. An improved optical packet switching （OPS） node structure based on recirculation optical fiber delay line （FDL） and feedback tunable wavelength converter （TWC）, and a specific scheduling algorithm for the node structure are presented. This switching structure supports both point-to-point and point-to-multi- points broadcasting transmission with superior capacity expansion performance. Its superiority in packet loss probability is proved by simulation.     

Wavelength division multiplexed loop buffer memory based optical packet switch

Photonic all-optical switching is widely considered as one of the technique to utilize the enormous optical bandwidth. Optical packet switching provides high speed, data rate transparency, data format transparency, efficient use of bandwidth and flexibility. To resolve the conflict during contention, packets are needed to be buffered. Due to the lack of optical RAM, fiber delay lines (FDLs) are the most suited option to buffer the packets. This paper proposes new optical packet switch architecture alongwith feedback shared buffer utilizing the advantage of WDM loop buffer memory. The loop buffer module used in this switch architecture is a new approach towards WDM buffering of packets. The mathematical modeling is done to validate the results obtained from simulation.     

Eu-Doped KCl storage phosphor for erasable and rewritable optical memory utilizing photostimulated luminescence phenomenon

Intense photostimulated luminescence (PSL) with a peak at 420 nm is observed in ultraviolet (UV) Iight-irradiated europium-doped potassium chloride (KCl: Eu) crystalline phosphors. The PSL characteristics of UV-irradiated KCl: Eu phosphor for optical memory application were studied. The excitation and emission mechanisms of the 420 nm PSL, which are consistent with the results obtained, are discussed.     

AWG and EDFA based optical packet switch using feedback shared loop buffer memory

Optical packet switching provides high speed, data rate/format transparency, efficient use of bandwidth and flexibility. The major problem in the implementation of “all-optical” switching is contention which occurs when two or more packets arrive at the same time for the same destination. To resolve the contention, we have proposed an optical packet switch architecture based on WDM loop buffer memory in the feedback configuration. In that architecture, the contending packets are stored in a loop buffer module, and routed in the free time slots. The buffering duration in the recirculating loop is limited by a circulation limit. The analysis was been done to obtain the maximum number of allowed circulations. This paper proposes improved version of that optical packet switch architecture, to increase the number of maximum allowed circulations. The modification is done either by adding an extra erbium doped fiber amplifier (EDFA) in the original switch or by replacing the core space switch with arrayed waveguide grating (AWG). The performance analysis has been done by the simulations.     

Slotted microcavity ring resonators for optical storage applications

In this paper, slotted microcavity ring resonators based optical storage devices are proposed and analyzed by means of multiresolution time domain technique. The effect of the structure geometrical parameters on the coupling efficiency, normalized transmission spectra and quality factor has been thoroughly investigated and compared to that of the conventional no-slot microring resonator. The suggested slotted configurations increase the quality factor at a fixed gap size between the central ring and input/output waveguides. In addition, the desired compromise between the coupling efficiency and resonance effect inside the ring can be achieved by mere optimization of the slot geometrical characteristics.     

Active optical storage ring for high-power laser pulses

In an optical storage ring, a dye laser amplifier synchronously pumped by external laser pulses has been implemented and experimentally tested. The test was done at =580 nm, but the optical system can be used without limitations in a broad band of 400–700 nm. It is shown that a selected turn of the stored laser pulse can be amplified by typically a factor of 200. Power consideration gives an increase of the efficiency of the optical storage ring with a dye amplifying cell, as compared to a single passage of the laser pulse through the experimental section, by 23 times and it is shown that it can reach a factor of more than 100. PACS 42.60.Da; 42.60.Lh     

High-power single-wavelength SOA-based fiber-ring laser with an optical modulator

A semiconductor optical amplifier (SOA) fiber-ring laser (SOAFRL) utilizing a fiber-Bragg grating (FBG) and lithium niobate (LiNbO₃) modulator is demonstrated. The laser operates at a wavelength of 1547.64 nm, which is equal to the Bragg wavelength in the saturation region. By removing the LiNbO₃ modulator in the ring, the laser shows a single-wavelength output, which has a lower peak power. The experimental results show that when reaching the saturation level, the system with the LiNbO₃ modulator shows a higher saturation current and peak power compared to that of the system without the modulator. The effect of varying the modulation frequency on the laser output power is investigated. By incorporating the LiNbO₃ modulator in the laser cavity, the side-mode suppression ratio (SMSR) of the laser is significantly improved and a higher peak power can be obtained at a higher current.     

A stable multiwavelength SOA-based fiber ring laser with ultra-narrow wavelength spacing

This investigation demonstrates a stable multiwavelength fiber ring laser with ultra-narrow wavelength spacing using a semiconductor optical amplifier (SOA). A delay interferometer and a mirror are used as a double-pass interferometer to improve the signal-to-noise ratio in this experiment. Up to 181 stable lasing wavelengths with a wavelength spacing of 10.7 GHz and a signal-to-noise ratio of over 24 dB are produced at room temperature.     

An optical multicast packet switching architecture shared with limited-range multi-wavelength converter and full-range wavelength converters

Optical packet switch with multicast capability can inspire a broad range of multipoint to multipoint applications in future optical networks. An optical multicast packet switching architecture, equipped with feedback shared small number of limited-range multi-wavelength converters (LMWCs) and output shared some full-range wavelength converters (FRWCs), is proposed for a wavelength-division multiplexed optical multicast network to improve multicast performance in the paper. The FRWCs are used to overcome the performance degradation in terms of packet loss probability due to only use LMWCs. In the architecture, the two converters are shared by all the multicast packets importing to the optical multicast switch node. A maximum bipartite matching with minimum edges weights strategy was designed to employ fewer wavelength converters and avoid useless degradation of optical signal quality for the architecture to improve the node performance. The simulation results show that the proposed architecture and its wavelength converter scheduling algorithm can reduce the multicast packet loss probability with relatively lesser wavelength conversion cost.     

Performance improvement for optical packet switch with shared buffers

In this paper, an inner wavelength method is proposed to enlarge buffering capacity of shared fiber delay line buffers. In addition, an optical packet switch called extended shared buffer type optical packet switch(extended SB-OPS) is proposed to realize the inner wavelength method. In order to further improve performance of extended SB-OPS, a greedy algorithm based on inner wavelength method is introduced.The performance of extended SB-OPS is evaluated by simulation experiments.     

Multiplexed phase-conjugate holographic data storage with a buffer hologram

We describe and demonstrate a volume holographic storage system in which a phase-conjugate object beam is reconstructed by the same reference beam that was used for recording. An intermediate hologram is used as a temporary buffer, recorded with its own reference beam and the data-bearing object beam. Reading this buffer hologram with the phase conjugate of its reference beam reconstructs the phase conjugate of the object beam, which can then be recorded into the desired volume hologram for long-term storage. This method combines the immunity to lens aberrations provided by phase-conjugate readout with the simplicity of using the same multiplexed reference beam for both recording and readout. Only a single pair of phase-conjugate reference beams is required. Experimental results are shown with a single LiNbO(3):Fe crystal used as both buffer and storage holograms and a self-pumped phase-conjugate mirror in BaTiO(3) that provides the pair of phase-conjugate reference beams.     

Photonics applications in switching: An ATM optical node

An ATM optical node architecture that carries out cell routing and buffering by photonic means, controlled by electronic circuits, is presented. An evolutionary approach, where cell aggregation and compression are introduced to achieve a large throughput, with a high performance, is also described. And we report experimental results that demonstrate the feasibility of all the relevant photonic functions, based on advanced optoelectronic devices, namely: fast wavelength reassignment, suitable for multigigabit operation, based on fast tunable lasers and semiconductor optical amplifiers; high bit rate packet storage in a multiwavelength fiber loop memory including fast optical gates; dynamic wavelength selection, based on distributed feedback (DFB) filters with nanosecond tuning response; and all optical demultiplexing of multigigabit/s time division multiplexing (TDM) signals by means of saturated semiconductor optical amplifiers.     

Toward a storage ring with no shear

One barrier to the attainment of a crystalline ordered state for a well-cooled beam in a storage ring will be the viscous heating by the shear induced in the bending fields of the ring. Shear will transfer some of the energy of coherent motion to thermal energy and may prevent reaching the very low temperatures required for formation of the ordered state. A concept for a ring is proposed in which shear within a monoenergetic beam of finite size is substantially reduced by means of combined electrostatic and magnetic fields within the bending elements.     

Photonics applications in switching: An ATM optical node

Abstract

An ATM optical node architecture that carries out cell routing and buffering by photonic means, controlled by electronic circuits, is presented. An evolutionary approach, where cell aggregation and compression are introduced to achieve a large throughput, with a high performance, is also described. And we report experimental results that demonstrate the feasibility of all the relevant photonic functions, based on advanced optoelectronic devices, namely: fast wavelength reassignment, suitable for multigigabit operation, based on fast tunable lasers and semiconductor optical amplifiers; high bit rate packet storage in a multiwavelength fiber loop memory including fast optical gates; dynamic wavelength selection, based on distributed feedback (DFB) filters with nanosecond tuning response; and all optical demultiplexing of multigigabit/s time division multiplexing (TDM) signals by means of saturated semiconductor optical amplifiers.     

4 x 4 optical cross-point packet switch matrix with minimized path-dependent optical gain

Packet-switching characteristics are optimized across an integrated 4 x 4 optical cross-point switch matrix based on active vertical coupler switch cells. Optical gain is demonstrated across the entire matrix with a <3-dB difference between the shortest and longest switching paths.     

Novel optical packet with non-return-to-zero label and duobinary carrier-suppressed return-to-zero payload

A novel packet format with non-return-to-zero (NRZ) label and duobinary carrier-suppressed return-to-zero (DCS-RZ) payload is proposed for optical packet switching networks.NRZ label is followed by DCS-RZ payload with a certain guard time.The spectra of the low-rate NRZ label locate around the optical carrier frequency where some parts of the corresponding spectra of the high-rate DCS-RZ payload have been suppressed due to DCS-RZ modulation.At the switching node,the label or payload extraction can be realized simply through an optical bandpass or notch filter respectively.The feasibility of the scheme is verified by the simulation on the famous photonic design platform designed by Virtual Photonics Inc.(VPI).The effects of optical filter bandwidth on the received signal quality are discussed by analyzing bit error rate(BER)and contrast ratio performances.     

Separation and insertion of optical bit-serial label in optical packet switching

The bipolar phase-shift-keying (BPSK) optical orthogonal codes (OOCs) are inserted into the optical packet format of bit-serial label. The ultra-fast separation of the label and payload is performed through the auto-correlation pulses indicating the time position at which the optical switch changes the state.The insertion of the new label can also be realized by detecting the auto-correlation pulse at the line rate. Especially, the scheme can be adapted to the asynchronous separation and insertion and realize the variable-length packet switching. The results of simulation verify the feasibility of the scheme.     

Hardness evaluation with an optical ring light

Evaluation of hardness by interrogating the residual indentation in a static test using a microscope can be hampered by poor image quality. Image digitization with processing may overcome this but is limited by cost, convenience, and speed. It is shown that the indented surface on the sample in a Brinell test acts effectively as a spherical mirror. Thus, placement of an optical ring light coaxial with the microscope objective and at varying distances from the sample surface produces a distinct right light image that can be correspondingly altered in diameter. The Brinell hardness can be computed by determining the ring light to sample distance after adjusting the ring light image diameter to equal the indentation diameter. This approach is verified experimentally and found to be accurate, cost effective, and expeditious.