Optical Tap Research Articles

Scalable quantum optical tap for the distribution of quantum information encoded in entangled fields

Scalable quantum optical tap for the distribution of quantum information encoded in entangled fields

Fiber-Based Inline Optical Tap With Tunable Wavelength and Bandwidths

Fiber-Based Inline Optical Tap With Tunable Wavelength and Bandwidths

Optimum quantum resource distribution for phase measurement and quantum information tapping in a dual-beam SU(1,1) interferometer.

Quantum entanglement is a resource in quantum metrology that can be distributed to two conjugate physical quantities for the enhancement of their measurement sensitivity. This is demonstrated in the joint measurement of phase and amplitude modulation signals in quantum dense metrology schemes. We can also devote all the quantum resource to phase measurement only, leading to the optimum sensitivity enhancement. In this paper, we experimentally implement a dual-beam sensing scheme in an SU(1,1) interferometer for the optimum quantum enhancement of phase measurement sensitivity. We demonstrate a 3.9-dB improvement in signal-to-noise ratio over the optimum classical method, and this is 3-dB better than the traditional single-beam scheme. Furthermore, such as cheme also realizes a quantum optical tap of quantum entangled fields and has the full advantages of an SU(1,1) interferometer, such as detection loss tolerance, making it more suitable for practical applications in quantum metrology and quantum information.

Broadband optical fiber tap based on cladding-mode coupling

We propose a broadband light-tapping technique, where an input fiber excites the cladding modes of an output fiber through a gap between the two fibers, and the cladding modes of the output fiber are transferred to a parallel tapping fiber through evanescent-field coupling between the two fibers. The tapping efficiency and the excess loss of the fiber tap depend on the fiber type and the gap distance between the input fiber and the output fiber. We demonstrate the technique with standard single-mode fibers and photonic crystal fibers and discuss its performance. The proposed tap configuration is applicable to practically any fibers and could be further developed into useful light-tapping devices or sensors.

Optical waveguide tap with low polarization dependence and flattened wavelength using a Mach–Zehnder directional coupler

The coupling length of a directional coupler is strongly polarization dependent, especially for use in waveguide tap monitoring applications. To avoid severe polarization and maximize the wavelength flatness of optical waveguide taps, a 12 μm thick silicon-on-insulator (SOI) platform and Mach–Zehnder directional couplers implemented with the bending effect illustrated low coupling loss to a SMF-28 fiber, low polarization dependence, and insensitive wavelength on the tap port for monitoring applications. Our results demonstrated that the optical waveguide tap, which carries a portion of the light signal, showed a 0.077 coupling ratio and 0.2 dB for the polarization-dependent loss. The wavelength variation for the coupling ratio was less than 4% across the entire C-band. A 0.26 dB per interface coupling loss was also achieved between the 12 μm thick SOI waveguide and the SMF-28 fiber.

Signal power tapped with low polarization dependence and insensitive wavelength on silicon-on-insulator platforms

The length of a directional coupler, including the straight and curved parts, is strongly polarization dependent, especially for use in waveguide tap monitoring applications. Three types of curved structure in the coupled regions are presented to demonstrate the different phase contributions in a directional coupler. A 12 μm thick silicon-on-insulator waveguide single-mode region was theoretically verified by using the beam propagation method, thereby significantly improving the polarization dependence and coupling loss with a conventional fiber. The Mach–Zehnder directional coupler made of a 12 μm thick silicon-on-insulator waveguide could minimize the severe polarization dependence on the optical tap port and achieve a flattened wavelength response by implementing the coupled phase effect from the directional coupler’s curved structures. The results demonstrated that the optical waveguide tap port, carrying a portion of the light signal, showed a 0.024 coupling ratio and 0.3 dB for the polarization-dependent loss at a 1550 nm wavelength. The wavelength variation in the tap splitting ratio and polarization was less than 1% and 0.6 dB, respectively, across the entire C-band. A 0.26 dB per interface coupling loss was also achieved between the 12 μm thick silicon-on-insulator waveguide and SMF-28 fiber.

Fabrication of pellicle beam splitters for optical bus application

The optical bus architecture for on-board applications requires a number of optical splitters with precise split ratios to route part of the input signal. Since hollow metal waveguide provides well collimated beams with very small gap loss, it opens the possibility of inserting discrete optical beam splitters (taps). The optical tap requires low excess loss, polarization insensitivity, temperature stability, minimized walk-off of the propagating beam, and cost effective manufacturing. By benefiting from the mature interference coating technology for polarization insensitivity and temperature stability, we design a pellicle beam splitter based on a static microelec tro-mechanical system (MEMS) and develop processes to fabricate pellicle splitters using wafer level bonding of silicon and glass substrates, with subsequent thinning to 20 µm. With the approaches described in this paper, we have demonstrated optical beam splitters with excess loss of less than 0.17 dB that operate at a data rate of 10 Gb/s showing a clean eye diagram while providing controlled split ratio and polarization insensitivity. We have demonstrated a high yielding MEMS based silicon processing platform which has the potential to provide a cost effective manufacturing solution for optical beam splitters.

High-Resolution Tunable Microwave Filter Using Hybrid Analog-Digital Controls via an Acoustooptic Tunable Filter and Digital Micromirror Device

A programmable broadband Radio Frequency (RF) filter is designed using a Digital Micromirror Device (DMD), an Acoustooptic Tunable Filter (AOTF), and a Chirped Fiber Bragg grating (CFBG). This hybrid analog-digital optical design enables implementation of RF filters with higher number of taps in comparison with an AOTF-only RF filter design and improved RF tunability in comparison with a DMD-only design. A 3-tap RF filter is theoretically analyzed and experimentally demonstrated using a combination of analog and digital optical tap selection. Filter nulls recorded at 6.90, 6.945, and 6.99 GHz show the tunability improvement with the hybrid design. Implementation of higher tap count filters can lead to similar improvements in filter tunability and pass-band and stop-band characteristics.

Low Loss Vertical Optical Path Conversion Using 45° Mirror for Coupling between Optical Waveguide Devices and Planar Devices

To realize low loss optical interconnects between optical waveguide devices and two dimensional array-type devices, we investigated a novel 45° mirror device buried by index matching epoxy resin and coated with an anti-reflection layer. A groove with an isosceles right triangle cross section was formed using a dicing saw so as to cut into the single-mode optical waveguide, and aluminum thin film was obliquely deposited on the 45° side wall of the groove to increase the reflectance. The groove was filled with a spin-coating of UV-curable epoxy resin to planarize the top surface, and low index polymer (Teflon) was formed on the top surface as the anti-reflection layer. The optimum depth of the groove for reducing shadowing of the deflected beam was analyzed. As a result the insertion loss of the 45° mirror was reduced 1.3 dB compared to the insertion loss of straight waveguide. In addition, a novel optical tap device is proposed and demonstrated using a similar fabrication process to that of the 45° mirror device. The isosceles right triangle-shaped groove was formed on the upper cladding layer so as to almost touch the core layer. After filling it in and finishing it with the epoxy resin and AR coating used in the 45° mirror device, the loss of the through port was reduced 0.5 dB compared to the insertion loss of straight waveguide and -14 dB (4.0%) of the optical power was transmitted to the tap port. Lastly as a model of the coupling between waveguide devices and two-dimensional arrayed devices such as vertical cavity surface emitting lasers (VCSEL's), the vertical port of the 45° mirror device was connected to a single mode fiber with a very small mode field diameter (3.6 µm). This configuration transmitted -11.8 dB (6.6%) of the input power from the input port to the vertical tap port and vice versa.

Control packet signaling mechanism using electronic code division multiple access for packet-based networks

We propose and experimentally demonstrate the feasibility of a control packet signaling technique using electronic code division multiple access for a wavelength division multiplexing packet-based network, whereby each wavelength channel is assigned a unique electronic code based label on a radio frequency subcarrier. Such a technique allows each wavelength channel to be electronically identified without requiring the use of a WDM demultiplexer. We experimentally demonstrate this technique with two wavelength channels each with 1.25 Gb/s baseband payload data and 10 Mb/s header coded onto an electronic code at 160 Mb/s. A performance study of the electronic code division multiple access based control signaling scheme in a wavelength division multiplexed packet-based access network is also performed in terms of the required power budget to monitor the electronic code division multiple access control signals in the presence of several sources of noise for error-free transmission of both payload data and electronic code division multiple access based control signals. It is shown that the modulation depth of each signal impacts the amount of required optical tap power. As the modulation depth of the electronic code division multiple access based control signal is increased, the required optical tap power is reduced. However, this increases the bit-error-rate for the payload data. Therefore, there lies a maximum and a minimum of the required tap optical power for the successful recovery of both signals. The lower bound of this range is usually determined by the successful recovery of electronic code division multiple access based control signal while the upper bound is determined by the successful recovery of payload data. The required optical tap power is analyzed for different transmission bit rates of the payload data for various receiver architecture scenarios without an optical amplifier at the receiver. The scalability analyses were repeated with an optical amplifier placed in the receiver terminal of the network. The resulting optical tap power that is required for the successful monitoring of the electronic code division multiple access based control signals are compared with that of the case without the amplifier.

Tapping Light From Waveguides by High-Order Mode Excitation and Demultiplexing

A novel high-performance optical tap with low wavelength-dependent loss(WDL), polarization-dependent loss (PDL), and excess loss is described. The tap is based on exciting a high-order mode by an abrupt change in the waveguide profile, and then tapping the optical power in the high-order mode by using a modal-demultiplexer. The tap can be designed to give a tapping ratio in the range of -30 to -10 dB over a wavelength range of 1510-1640 nm. In addition, it is shown that the tapping ratio is tolerant to process variations, repeatable and predictable, enabling the design to be implemented in a single process run, with no need for additional fine-tuning iterations, while achieving a high process yield. We show that measurements are in good agreement with simulated results. In the tap channel we measured 0.3 dB WDL and 0.2-dB PDL over the C- and L- bands, while the signal in the main channel was virtually uncontaminated relative to a plain single-mode reference waveguide.

Single quadrature duplication and transparent taps

The concept of single quadrature duplication, which is the process of producing two outputs with the same homodyne detecting statistics as an input, is addressed. This device has important potential application to optical communications as a transparent optical tap in a local area network environment. The characteristics of the device are examined, and a realization scheme employing a coupler and phase-sensitive amplifiers is proposed.

Design and analysis of an optical waveguide tap for silicon CMOS circuits

A compact low-loss optical tap technology is critical for the incorporation of optical interconnects into mainstream complementary metal-oxide-semiconductor (CMOS) processes. For this work, an effort has been made to establish an optimal integrated optical tap design in terms of optical loss, bandwidth, economy, and process compatibility with multimetal layer CMOS circuits. A new device, which is based on a variation of the multimode interference effect, has been found to be especially promising. Two-dimensional (2-D) and three-dimensional (3-D) simulation results show low excess optical loss (<0.1 dB) for the design, and a nominal 40% (2.2 dB) optical coupling into the CMOS circuitry over a wide range of guide to substrate distances. Simulated tap devices are on the order of 15 [tin in length. Polymer waveguide materials are targeted for tap fabrication due to planarization properties, low cost, broad index control, and poling abilities for modulation-tuning functions. Low-cost silicon CMOS-based processing makes the new tap technology especially suitable for computer multichip module and board level interconnects, as well as for metro fiber to the home and desk telecommunications applications.

Feedback controlled variable optical attenuatorfor channel power regulation in WDM systems

A variable optical attenuator is described which uses an asymmetric polymeric Y-branch waveguide. It incorporates an optical monitoring tap to regulate the optical output regardless of variations in input light power and polarisation. The dynamic attenuation range was > 18 dB at 1.55 µm. The attenuator was successfully used to regulate channel powers within 0.5 dB in a WDM system.

Polymeric tunable optical attenuator with an optical monitoring tap for WDM transmission network

A polymeric tunable optical attenuator has been fabricated using asymmetric Y-branch waveguides integrated with an optical monitoring tap. One arm of the branch serves as the main output port, while the other arm helps remove the residual optical power resulting from attenuation. An optical power tap used for the monitoring port is introduced to take a fraction of the main port power. This monitoring port is useful for observing the main output continuously. Furthermore, it can be fed back to the electrical driver to maintain the attenuated output regardless of variations in input light polarization and power. By utilizing the modal evolution effect in asymmetric branches, the attenuator has enhanced fabrication tolerance and reduced wavelength sensitivity. Also, no electrical bias is needed to achieve maximum optical transmission. The attenuator exhibited a dynamic range of more than 20 dB at 1550 nm and a response time of about 1 ms. The polarization dependent loss was about 0.9 dB, and the wavelength uniformity was less than 1.2 dB over the range of 1530-1560 mm.

Implementation of an optical TAP: preliminary results

The FIM Group of the University of Rouen is developing a new type of detector that can be used in atom probe and 3D atom probe applications. This detector consists of an array of conductive and transparent strips covered with a phosphorescent material. After having produced light, electrons generated by ionic impacts onto microchannel plates produce signals on strips that are used for timing. At the same time, light produced by ions on the phosphor screen is recorded by means of a CCD image sensor. Then, the comparison between positions and the distribution of time of flight on the strip array makes it possible to correlate positions and times for each event. In this contribution, preliminary results obtained with a 5×5 cm 2 detector having eight strips will be shown. Potential capabilities and performance will be discussed.

Quantum Nondemolition Measurements Improved by a Squeezed Meter Input

Continuous quantum nondemolition (QND) measurements of the amplitude quadrature of a 1064 nm wave are performed with a monolithic dual-port degenerate optical parametric amplifier (OPA). The quality of the measurement is limited in part by the quantum fluctuations carried by the vacuum meter input wave. Improved QND measurements are realized by injecting 3.4 dB amplitude-squeezed light into the meter input port of the OPA. This achieves increased squeezing and correlation of the output signal and meter waves, and both improved operation as a quantum optical tap and as a quantum state preparator. The all-solid-state system was operated for 5 h with high stability.

Continuous-wave quantum nondemolition measurements with vacuum and nonclassical meter input

QND measurements of the amplitude quadrature of continuous-wave light are performed with a monolithic dual-port degenerate optical parametric amplifier (OPA). Operated with a vacuum meter input, both output beams are squeezed and 33% correlated, demonstrating individually squeezed twin beams. The sum of the signal and meter transfer coefficients is 1.05, demonstrating operation as a quantum optical tap. The device exhibits quantum state preparation ability for both signal and meter output, reaching the conditional variances of \(-0.8\) dB and \(-2.5\) dB, respectively. An improved quantum measurement is realized by injecting 3.4 dB amplitude-squeezed light into the meter input port of the OPA. This achieves increased correlation and squeezing of the output beams, and both improved operation as a quantum optical tap and as a quantum state preparator. The all-solid-state system was operated for up to 5 hours with high stability.

Narrow-beam aluminum-mirrored fiber optical-taps with controllable tapped power

A fiber optical-tap has been fabricated and tested. Two separate fiber tips were polished with an angle of 45/spl deg/, and one of the tips was coated with aluminum inside a vacuum deposition unit. Then, the coated and uncoated polished tips were spliced together using a fusion splicer to form a fiber optical-tap. The power of the tapped light is controllable by controlling the thickness of the aluminum coating during vacuum deposition. As the aluminum coating thickness increases, the amount of tapped light increases and consequently the power transmitted after the fiber optical-tap decreases. For the same aluminum coating thickness, the tapped beam power from a single-mode fiber tap is higher than that from a multimode fiber tap. In addition to the feasibility of tapping a narrow light beam and controlling its power, the fabricated optical tap has a short length, which means that it can be integrated easily in optical signal-processing circuits. The mechanical strength of the tap has been tested in the laboratory and found to be capable of supporting between 75 and 180 g before breaking.

A 1.3-μm wavelength laser with an integrated output power monitor using a directional coupler optical power tap

A 1.3-/spl mu/m Fabry-Perot laser with a directional coupler power tap inside the laser cavity, used for diverting optical power to an integrated waveguide monitoring photodetector is demonstrated. The monitoring detector provides photocurrent which is linear with the front facet output power, with responsivity as high as 0.37 mA/mW, depending on the length of the directional coupler coupling region.