Optical Fiber Delay Lines Research Articles

Demonstration of feed-forward control for linear optics quantum computation

One of the main requirements in linear optics quantum computing is the ability to perform single-qubit operations that are controlled by classical information fed forward from the output of single-photon detectors. These operations correspond to predetermined combinations of phase corrections and bit flips that are applied to the postselected output modes of nondeterministic quantum logic devices. Corrections of this kind are required in order to obtain the correct logical output for certain detection events, and their use can increase the overall success probability of the devices. In this paper, we report on the experimental demonstration of the use of this type of feed-forward system to increase the probability of success of a simple nondeterministic quantum logic operation from approximately $\frac{1}{4}$ to $\frac{1}{2}.$ This logic operation involves the use of one target qubit and one ancilla qubit which, in this experiment, are derived from a parametric down-conversion photon pair. Classical information describing the detection of the ancilla photon is fed forward in real time and used to alter the quantum state of the output photon. A fiber-optic delay line is used to store the output photon until a polarization-dependent phase shift can be applied using a high-speed Pockels cell.

Technique for detecting changes in fluorescence lifetime by means of optoelectronic circuit auto-oscillation

We present a new, simple, inexpensive, and highly precise approach to excited-state fluorescence-lifetime-based measurements. The detection system consists of a closed-loop optoelectronic arrangement containing a radio frequency resonance amplifier, a fluorescence excitation light source, a fiber-optic delay line, and a photodetector. The system exhibits auto-oscillations in the form of intensity modulation. The oscillation frequency varies with the modulation phase shift of the fluorescent light. This frequency is used as the detection parameter, which is advantageous because frequency may be measured easily, inexpensively, and with high precision. This technique is well suited for chemical or biosensor applications.

A Scalable and High Capacity All-Optical Packet Switch: Design, Analysis, and Control

In this paper, a modular and scalable all-optical packet switch (AOPS) is proposed. The range of its capacity can be easily scaled from gigabit per second to multi-terabits per second. Due to its broadcast-and-select property, the proposed AOPS is capable of performing a multicast function. By taking the advantage of wavelength division multiplexing (WDM), this architecture can provide the best network performance using a limited number of optical fiber delay lines as buffers. To perform the header replacement function, a novel all-optical header replacement unit (HRU) is introduced to be integrated with the switching function. The proposed HRU is shared by all the inputs which provides cost advantages. In addition, we present a generic control scheme for the proposed AOPS. To implement the function of the AOPS, two possible approaches, based on the design of wavelength conversion pools (WCPs), are presented and their cascadability performances are compared. Our simulations show that the proposed AOPS with an arrayed waveguide grating (AWG) based WCP provides better cascadability performance than the one with a star coupler based WCP. We conclude that, based on the status of current optical and electronic technologies, the proposed architecture is feasible to be implemented, and can be a good candidate for future packet switching solutions.

Cascading prism dispersion [phased array antenna

There have been numerous efforts to use fiber-optic techniques in array antennas. Fiber-optics is attractive for the same reasons it is the technology of choice for telecommunications applications. Advantages include: a natural resistance to electromagnetic interference (EMI), low weight, small size, low intrinsic losses and the ability to easily remote components. Additionally, its unique processing capabilities permit simplifying the arrays and adding system functionality, e.g., dynamic beam shaping (adaptive beamforming) and time-steering. A wide variety of optical implementations have been proposed for time-steered array antennas. The Naval Research Laboratory (NRL) has developed a practical, fiber optic technique for implementing time-steered arrays. The approach is based upon a dispersive, fiber-optic delay line combined with a simplified beamforming architecture. This method solves many of the problems associated with optical true time delay (TTD) beamformers. It has been dubbed the fiber-optic dispersive prism. The basis for the approach is shown.

On-the-Fly Fluorescence Lifetime Detection in Liquid Chromatography with Data Collected Simultaneously at Multiple Emission Wavelengths

A novel liquid chromatography (LC) fluorescence detector simultaneously generates fluorescence decay curves at multiple emission wavelengths. The fourth harmonic (266 nm) excitation light from a pulsed Nd:YAG laser is focused into a standard LC flow cell. A small spectrograph disperses the fluorescence. Fiber-optic delay lines positioned in the exit focal plane time the arrival of photons at the photomultiplier tube detector. Four wavelength channels with 50 ns channel spacing were used in this study. The intensity-decay time waveform is averaged with a digital storage oscilloscope. Temporal overlap between adjacent wavelength channels is removed during the post-processing of the data. System performance was characterized for chromatographic elution of polycyclic aromatic hydrocarbons (PAHs). Detection limits are 1.6 ppb for naphthalene and 0.14 ppb for fluorene. Resolution of co-eluting 1,4-dimethyl-naphthalene and anthracene components on the basis of differences in their lifetimes and spectral distributions is demonstrated.

Optical fibre delay line filter free of limitationimposedby optical coherence

The authors propose a novel technique for overcoming the limitation of the frequency response of an optical fibre delay line filter imposed by optical coherence. A high birefringence fibre based filter is demonstrated, giving a response free of optical interference noise and tunable by temperature.

Analysis of Chromatic Dispersion Variation in Optical Fiber under Large Stretching

In the frame of a large-stroke optical fiber delay line implementation, using the ability of silica fibers to induce large and variable group delay when they are stretched, we intend to express theoretically the evolution of second-order chromatic dispersion versus fiber stretching. Both an experimental analysis and a numerical analysis are presented in this paper. The main result consists of the observation of a linear variation of the second-order chromatic dispersion versus a 0 to 32-cm group delay variation. The numerical simulation exhibits a discrepancy of 10% with respect to the experimental results.

Reconfigurable fiber-optic delay line filters incorporating electrooptic and electroabsorption modulators

The authors propose and demonstrate experimentally a novel class of flexible and fastly reconfigurable fiber optic delay line filters for microwave signal processing that incorporate electrooptic and electroabsorption modulators as weighting elements.

A novel wide-band tunable RF phase shifter using a variable optical directional coupler

We present a novel RF phase-shifter design with a usable bandwidth of 80:1. The design is verified through demonstration of a proof of concept device, consisting of a readily available voltage variable optical coupler fabricated from LiNbO/sub 3/, combined with an fiber-optic delay line. The design is analyzed theoretically and measurement of the device confirms the predicted range of operation. Methods of extension of this range of operation are discussed.

High-performance, low-cost fibre optic delay lines for analog applications

A fiber optic delay line is designed, built, and tested using directly modulated semiconductor laser diodes operating at a 1.3 μm wavelength. Delays of 10 μs are demonstrated, with a spurious free dynamic range of up to 59 dB, in the 200 MHz bandwidth (114 dB/Hz2/3), within the 0.7–1.4 GHz modulation band. A wide-frequency bandwidth of up to 6 GHz is also reported, which results in a pulse response in the fiber optic link of 180 ps, with very low pulse distortion. Also, testing of the semiconductor optical amplifier in the fiber link is reported. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 20: 173–177, 1999.

Polarization control in a large-stroke optical fiber delay line

In the context of an optical fiber delay-line implementation by use of silica fiber stretching capability, we experimentally demonstrate that highly birefringent fibers preserve their ability to maintain the polarization coherence in spite of the high magnitude of the stresses applied to them during large stretching. Two experimental demonstrations are presented. In the first, polarization cross coupling versus stretching is characterized. This stretching induces a variation of group delay in the span 0-45 cm. The second is a test of the fiber stretcher in an interferometric application.

Characterisation of the dispersion evolution versus stretching in a large stroke optical fibre delay line

In the frame of a large stroke optical fibre delay line implementation, we report experimental work focused on the full analysis of chromatic dispersion evolution versus fibre stretching. The delay line is tested in a Mach–Zehnder interferometer. The experimental work is carried out using a spectral analysis of the interferometric mixing. A linear variation of the second-order chromatic differential dispersion is observed versus high stretching. The stretched fibre dispersion evolution is scaled by comparison with unstretched fibre samples generating an equivalent group delay.

All-optical regenerative memory with full write/read capability

We demonstrate an all-optical regenerative memory with the capability to write and read optical pulses at any time slot in an optical fibre delay line. The memory architecture comprises three TOAD optical switching gates.

Tunable optical delay line based on a fibre Bragggrating

A tunable fibre optic delay line is demonstrated using a uniform fibre Bragg grating. A segment of the grating is heated, increasing its Bragg wavelength so that a signal propagating outside the nominal stop-band is reflected from that point. The position of the heater along the length of the grating determines the time delay encountered by the signal. For a 10 cm apodised grating, a delay of up to 700 ps was obtained.

Long time-base temporal holography using fiber-optic tapped delay line diffractive arrays

We propose a temporal holography technique for realizing matched filter structures for arbitrary, narrow-band optical signals. By utilizing the extraordinarily large angular dispersion of a fiber-optic tapped delay line array, we show that it is possible to achieve temporal filtering of optical signals whose coherence times can exceed nanoseconds. This represents a significant improvement in the temporal reach of holographic filters, compared to grating-based methods.

Packet error analysis of an all-optical packet switching node using a fiber-optic delay line matched filter as an optical packet address processor

The packet error rate of an all-optical packet switching node using a fiber-optic delay line matched filter as an optical packet address processor has been evaluated. The simulation results show that the average optical power at the input of the optical packet address processor increases as the number of "1" bits in the address field increases at a fixed packet error probability. This indicates that the shot noise due to correlation output pulse levels of the fiber-optic delay line matched filter becomes dominant for address code sets to accommodate more nodes in all-optical packet switching networks.

Future airborne optical fiber communication networks with single‐wavelength and multi‐wavelength code‐division multiple access techniques

AbstractWe design optical fiber code‐division multiple‐access (CDMA) networks to support future airborne high‐speed communication services (e.g., real‐time command and control communications). The proposed airborne communication networks have a full tunability and a fast reconfiguration time. This can support real‐time sensor data distribution and computer interconnects. Architectures for fastly tunable optical CDMA encoders and correlators using prime codes are presented, and their simple delay control logic is described, which can be easily performed by using optical fiber delay lines. Moreover, multi‐wavelength optical CDMA networks using a multi‐star topology are designed. It is shown that the use of multi‐wavelength OCDMA not only can reduce the power loss of encoders/correlators and the bandwidth expansion of optical CDMA, but also can separate avionics subsystems into groups according to different traffic requirements and data rates. This in turn can efficiently integrate several networks with different data rates and number of users into a single‐fiber network by using wavelength‐division multiplexing scheme, and new avionics subsystems can be feasibly added to such a single‐fiber network by assigning, for example, new wavelengths or additional optical CDMA codewords to facilitate future aircraft applications.

Optical packet compressor for ultra-fastpacket-switched optical networks

Based on a feed-forward fibre-optic delay line structure, a 16 bit optical compression technique is demonstrated for ultra-fast packet-switched optical networks. An incoming bit rate of 100Mbit/s is converted to an outgoing bit rate of 100Gbit/s with 10.0 ± 0.9ps bit spacing.

A 2 m stroke optical fibre delay line

We report the implementation of an optical fibre delay line demonstrating the capability of stretched silica fibre to induce a large and variable group delay. A metric delay line with a total stroke of 2.04 m has been tested in a Mach - Zehnder interferometer in the spectral domain. The induced waveguide losses are very low. At the present time the polarization and the dispersion effects are not corrected.

FRONTIERNET: frequency-routing-type time-division interconnection network

This paper describes a photonic time division multiplexing (TDM) highway switch, called FRONTIERNET, that uses optical frequency as routing information. This switch architecture can be applied to asynchronous transfer mode (ATM) switching systems. The N/spl times/N switch consists of N tunable frequency convertors and N frequency-division-multiplexed (FDM) output buffers connected through an N/spl times/N frequency router. The router can interconnect N input highways with N output highways in a completely noninterfering way. It is possible to address each output highway uniquely by the choice of frequency (frequency routing) and each output highway can receive any given frequency from only one input. This switch architecture therefore has three advantages: its novel output buffering scheme achieves the best possible performance, there is no need for a complicated contention resolution mechanism between input highways, and there is no splitting loss of the transmitted optical power. An experimental switch with a one-cell FDM buffer was constructed. The tunable frequency convertor based on fast tunable frequency lasers can transmit high-speed optical cells to which frequencies are assigned on a cell-by-cell basis. The frequency router is an integrated-optic arrayed-waveguide grating 16/spl times/16 filter produced by using planar-lightwave-circuit (PLC) technology. The one-cell FDM output buffer based on optical fiber delay lines can store FDM cells and select only one cell at each timeslot over the output highway. A 2.5-Gb/s experimental switch was successfully operated, And an experimental FDM loop buffer was also demonstrated. This stores two cells at a data rate of 2.5 Gb/s. The bit error rate (EER) of the cells after up to 10 circulations is <10/sup -9/. The performance of the buffer in terms of the probability of cell loss and the cell wafting time in the buffer is analyzed numerically. It is concluded that fewer optical buffers are needed to satisfy the desired probability of the cell loss compared with the conventional electronic buffers. The scale of the switch can be expanded in a modular fashion in two ways using a multistage frequency router and a multistage switching network. And the multihop FRONTIERNET architecture is proposed to reduce the required frequency channels rather than the single-hop FRONTIERNET. The switch scale is also very easy to expand by connecting the frequency-router-based switching submodules.