Fiber Optic Switch Research Articles

Field measurement of atmospheric CO₂ column abundance based on portable laser heterodyne radiometer

This study presents a portable near-infrared laser heterodyne radiometer specifically designed for measuring the column abundance of atmospheric carbon dioxide (CO₂) in the Taiyuan area. The instrument modulates the solar radiation using a fiber optic switch and amplifies the solar radiation through a semiconductor optical amplifier. The local oscillator laser is progressively scanned at the strong absorption characteristic of 1572.02 nm. Two beams of light are mixed on the photodetector to produce a heterodyne signal. To enhance performance, the radio frequency (RF) circuit system of the radiometer was thoroughly optimized, including adjustments to the filter bandwidth and the integration time of the lock-in amplifier. These improvements significantly enhanced the spectral signal-to-noise ratio (SNR) to a high level of 130 and achieved a spectral resolution of 0.0083 cm⁻1. The laser heterodyne signals were demodulated using a lock-in amplifier. Furthermore, a forward model based on line-by-line integration and an iterative fitting algorithm were employed to achieve high-precision CO₂ column abundance calculations. Outdoor field measurements conducted at Shanxi University validated the feasibility and practicality of this approach, laying a solid foundation for its broader application.

Multiple soliton operation in Ge2Sb2Te5 saturable absorber based fiber lasers

With the rapid development of fiber lasers, the invention of novel ultrafast modulators based on the new materials is critical for furthering basic research and practical applications of mode-locked fiber lasers. Ge2Sb2Te5 is a kind of phase-change and thermoelectric material. The fields of optical fiber temperature sensors, optical switches, and phase-change memories have all made extensive use of Ge2Sb2Te5. Nevertheless, the performance of Ge2Sb2Te5 is currently unproven in nonlinear optics and ultrafast laser applications. In this study, Ge2Sb2Te5-based saturable absorbers (SAs), were successfully prepared by depositing nanosheets on a tapered optical fiber. Conventional solitons, second-order harmonic mode-locked, and double-, triple-, quadruple-, and quintuple-pulse phenomena at different net dispersions are observed. A conventional soliton was obtained at 166 mW-987 mW with a pulse interval of 102 ns and a signal-to-noise ratio of 59 dB. At 440 mW of pump power, second-order harmonic mode-locked with a 3 dB bandwidth of 3.29 nm was obtained. The experimental results show that Ge2Sb2Te5 has a broad research prospect in designing ultrafast photonic devices in the future by virtue of its low cost, narrow bandgap, high damage threshold and high stability.

Spatial and mode selective switch for orbital angular momentum mode division multiplexing.

In analogy to a wavelength selective switch in wavelength-division multiplexing (WDM) optical fiber communication systems, a spatial and optical mode selective switch (SMSS) would be an important component in future ultrahigh capacity optical fiber communication systems based on space and mode division multiplexing. In this work, a free-space SMSS for orbital angular momentum (OAM) mode-division multiplexing (MDM) is proposed and experimentally demonstrated. The SMSS consists of a separating part for transforming OAM modes to spatial modes and a recombining part for selecting and recombining the modes to any spatial channel. The SMSS is able to implement strictly non-blocking switching between a total of 36 SDM/MDM channels configured as four spatial channels each supporting nine OAM mode channels.

Simultaneous atmospheric CH4, CO2 and O2 detection using fiber-optic switch (FOS)-based time-division multiplexed NIR laser long optical path absorption spectroscopy

A near-infrared (NIR) distributed feedback (DFB) laser sensor based on long optical path absorption spectroscopy technique was developed for simultaneous measurement of atmospheric methane (CH4), carbon dioxide (CO2) and oxygen (O2). A fiber-optic switch (FOS) in conjunction with the time-division multiplexing (TDM) technique was adopted to enable different lasers scan over the target gas absorption lines in turn. The long optical path wavelength modulation spectroscopy (WMS) technique with second harmonic detection as well as a laser power fluctuation correction method was used to improve the sensor’s precision and accuracy. For the selected gas absorption lines, located at 6046.945 cm-1, 6361.245 cm-1 and 7877.647 cm-1, the detection limit (1σ) of 0.034 parts per million (ppm) for CH4, 11.921 ppm for CO2 and 0.14% for O2 was achieved according to the concentration and noise level. Allan deviation analysis indicates that the 1-s measurement precision was 0.030 ppm for CH4, 11.518 ppm for CO2 and 0.14% for O2, which could be improved to 6.5E-4 ppm, 0.255 ppm and 0.005% at an optimal average time of 800 s. A two-day continuous measurement of the CH4, CO2, and O2 concentration from ambient air was carried out, which verifies the stability and robustness of the developed multi-gas sensor.

Wide-field-of-view auto-coupling optical antenna system for high-speed bidirectional optical wireless communications in C band.

Due to a great many superior features of infrared light communication (ILC), like high capacity and strong privacy, ILC is considered a potential candidate for serving the high demands of beyond fifth-generation/sixth-generation (B5G/6 G) communication systems. However, the terminal's limited field-of-view (FOV) induces great difficulty in establishing line-of-sight (LoS) link between the transceiver and the terminal. In this paper, we propose a wide-FOV auto-coupling optical antenna system that utilizes a wide-FOV telecentric lens to collect incident infrared beams and automatically couple them into a specific single-mode-fiber (SMF) channel of fiber array and optical switch. The performance of this optical antenna system is assessed through simulation and manual alignment operation, and validated by automatic alignment results. A coupling loss of less than 10.6 dB within a FOV of 100° for both downstream and upstream beams in C band is demonstrated by the designed system. Furthermore, we establish a bidirectional optical wireless communications (OWC) system employing this antenna and a fiber-type modulating retro-reflector (MRR) system in the terminal. Both 10-Gbps on-off keying (OOK) downstream and upstream transmissions are successfully realized with the FOV of up to 100° in C band where the measured bit-error-rate (BER) is lower than 3.8 × 10-3. To the best of our knowledge, this is a brand-new auto-coupling optical antenna system with the largest FOV in ILC automatic alignment works in terminals that have ever been reported.

Optical-Switch Raman Spectroscopy for High Throughput Screening

Although surface-enhanced Raman spectroscopy (SERS) is a powerful analytical technique with unbeaten sensitivity, the capabilities of SERS have been not fully utilized in screening applications because throughput of spectrum detection by conventional Raman instruments has been restricted due to their single-point measurement manners. Hence, this paper presents a development of a high throughput Raman screening system that employs a fiber-optic switch and a Raman probe array. In the system, a 785 nm excitation light is directed into the 1 × 8 broadband optical switching device and selectively switched to one of 8 output ports connected to the corresponding Raman probe array to deliver the light to samples under each probe. This optical switching driven probing in sequence allows us to rapidly detect Raman scattering of the multiple (n = 8) samples in array within a short time (~ 28 s) with decent sensitivity (10–7 M). The Raman spectroscopy of the system is validated by comparing the features of Raman spectra obtained from vitamin C tablets with those from a commercial Raman microscope and the detection sensitivity is measured with SERS substrates with different concentrations. Then, feasibility of high throughput screening is tested with a SERS chip array.

Optical Switching in Future Fiber-Optic Networks Utilizing Spectral and Spatial Degrees of Freedom

Forthcoming capacity scaling requirements of optical networks and advances in optical fiber communications beyond the omnipresent single-mode fiber operating over the conventional band introduces new opportunities and challenges for exploiting the expanded spectral and spatial resources available for fiber-optic network designs. The spectral and spatial degrees of freedom introduce utilization tradeoffs that can be leveraged under different applications. After briefly reviewing the supporting network building elements (emerging fiber types, multiplexers, optical switches, and amplifiers), we consider networking scenarios such as intra/inter datacenter, terrestrial, undersea, and wireless 5G/6G hauling networks and identify the best utilization plan and key attributes that can be harnessed by the offered spectral and spatial degrees of freedom for each scenario and how optical switching can be employed therein for traffic management. Networks supporting these scenarios are experiencing tremendous traffic growth pushing their existing implementations to their physical capacity-distance limits. New network builds must offer significant capacity multipliers in an efficient and cost-effective manner, requiring new switching solutions for supporting the unabated traffic growths foreseen in the years to come. We discuss how space-division multiplexed networks can help address this challenge in key communication scenarios.

Design of a temperature-control optical switch based on conjoined-tubular anti-resonance fiber with toluene core

In this paper, a temperature-control optical switch is designed based on a conjoined-tubular anti-resonance optical fiber (CTF). The CTF adopts eight pairs of conjoined tubes and four vertical-layout holes were coated with Au to increase the fiber confinement loss (Loss). Toluene was used as transmission medium to injected into the CTF core. The proposed switch produces a Loss difference over 100 dB and ER more than 30 dB. Influence of switch material refractive index and structural parameters on optical switch performance was further discussed. The proposed optical fiber switch has the features of simple structure, small size, broad working wavebands and adjustable operation temperature, which promises broad application prospects in industry, chemistry, biology and other fields.

Efficient use of expensive components of optic vibration sensor

This paper studies possible utilization of fiber optic switches for more efficient utilization of expensive electronic components which are the core of long range fiber-based sensors systems. Complex architecture of such systems starting to be used for monitoring of events along various linear objects like railway lines, product lines or object defense perimeters, are based on rather expensive ultra narrow band laser source and interrogation electronics. Possible sharing of these expensive components for sensing on more fiber optic lines is discussed in this work.

Design and Fabrication of a MEMS Electromagnetic Swing-Type Actuator for Optical Switch.

A microelectromechanical systems system (MEMS) electromagnetic swing-type actuator is proposed for an optical fiber switch in this paper. The actuator has a compact size of 5.1 × 5.1 × 5.3 mm3, consisting of two stators, a swing disc (rotator), a rotating shaft, and protective covers. Multi-winding stators and a multipole rotator were adopted to increase the output torque of the actuator. The actuator’s working principle and magnetic circuit were analyzed. The calculation results show that the actuator’s output torque is decisive to the air gap’s magnetic flux density between the stators and the swing disc. NiFe alloy magnetic cores were embedded into each winding center to increase the magnetic flux density. A special manufacturing process was developed for fabricating the stator windings on the ferrite substrate. Six copper windings and NiFe magnetic cores were electroplated onto the ferrite substrates. The corresponding six magnetic poles were configured to the SmCo permanent magnet on the swing disc. A magnetizing device with a particular size was designed and fabricated to magnetize the permanent magnet of the swing disc. The actuator prototype was fabricated, and the performance was tested. The results show that the actuator has a large output torque (40 μNm), fast response (5 ms), and a large swing angle (22°).

Development of real‐time vibration measurement system by fiber Bragg gratings with pulse light

AbstractWe developed a vibration measurement system by fiber Bragg gratings (FBGs) with a pulse light. The pulse light is produced by modulating a broadband light with an optical fiber switch at a modulation frequency of 40 kHz. This system enables to separate and detect reflection signals from multiple FBGs like a pulse train. This system achieves multipoint and real‐time vibration measurement by FBGs with a time resolution of 25 µs.

High-Capacity Super-Channel-Enabled Multi-Core Fiber Optical Switching System for Converged Inter/Intra Data Center and Edge Optical Networks

The introduction of the space domain in optical communications, collectively referred as space division multiplexing (SDM), have recently gained a lot of research attention motivated by the capacity exhaustion of conventional wavelength division multiplexing (WDM) systems. SDM not only increases the capacity, but also introduces new challenges and opportunities owing to the properties of the spatial channels in the form of fiber cores, modes or a combination of both. One promising application of SDM systems could be in future edge optical networks, where multi-core fibers (MCFs) with low inter-core crosstalk may be used with packet spatial super-channels (pSSCs) and core-joint SDM optical switches in a time-slotted network. We first briefly review the state-of-the-art of SDM transmission systems and other important technologies for edge networks such as burst-mode transmission. Finally, we focus on two recent experimental demonstration of such a switching system, achieving a capacity of 53.3 Tb/s for 7 spatial channels and QPSK modulation formant and an upgraded version with 8 spatial channels and 8PSK modulation format that achieves 83.33 Tb/s.

Experimental Study of Hollow-Core Photonic Crystal Fiber Optical Switching Effect in Liquid Nitrogen Environment

In this study, the hollow-core photonic crystal fiber (HC-PCF) optical switching effect in liquid nitrogen (LN2) environment is demonstrated and experimentally investigated. Turning off the light transmission is realized by the liquefaction of air present in the airholes of the HC-PCF when the fiber is immersed in LN2, and turning on the light transmission is realized by the evaporation of air when the fiber is taken out of LN2. The extinction ratio of the optical switching effect is found to be ∼50 dB; furthermore, the turn-on and turn-off time of the optical switching effect can reach ∼8 s and ∼3 s, respectively. Thus, optical switching effect in a HC-PCF in LN2 environment can be easily realized, which is beneficial in building all-fiber in-line low-frequency optical-switching systems that can be potentially applied in areas such as fiber sensors.

A fibered near-infrared laser heterodyne radiometer for simultaneous remote sensing of atmospheric CO2 and CH4

The performance of an all fibered near-infrared laser heterodyne radiometer (NIR-LHR) is demonstrated in ground-based solar occultation mode. A 1 × 2 fiber optical switch is employed as an alternative modulator to traditional chopper, which makes the system more stable and compact. Two distribute feedback (DFB) lasers centered at 1.6 μm and 1.65 μm, are employed as local oscillators to probe absorption lines of CO2 and CH4, respectively. After data processing and retrieval, column-averaged abundances and the mixing ratio of atmospheric CO2 and CH4 are determined based on the measurement of over six months in our laboratory (Hefei, China, 31.9°N 117.16°E). Finally, the results are validated by comparison with the GOSAT results during the same time period. The reported all fibered laser heterodyne radiometer in this manuscript has great potential to be a portable and high spectral resolution instrument for atmospheric remote sensing of multi-component gases.

Portable and automated fluorescence microarray biosensing platform for on-site parallel detection and early-warning of multiple pollutants

The portable and automated fluorescence microarray biosensing platform (FMB) that employed a compact hybrid optical structure, microfluidics, and microarray biosensors was constructed for on-site parallel detection of multiple analytes. In the FMB, a hybrid optical structure that composed of a 1 × 4 single mode fiber optic coupler, four fiber optic switches, a single-multi mode fiber optic bundle coupler was at the first time developed for the transmission of the excitation light and the collection and transmission of multi-channel fluorescence signals. Through the control of fiber optic switches, the parallel fluorescence assay of four channels could be achieved using only one excitation light and one photodiode detector on the basis of the time-resolved effect. This optical design not only greatly increased the efficiency of light transmission and fluorescence collection and detection sensitivity of the FMB, but also allows the miniaturization and portability of the whole system because of few optical separation elements used and no requirement of rigorous optical alignment. Taking Microcystin-LR (MC-LR), 2,4-D, atrazine (ATZ), and bisphenol A (BPA) for example, the application potential of the FMB to rapidly and parallelly detect four typical pollutants in real water with high sensitivity and specificity was demonstrated. The limits of detection of MC-LR, 2,4-D, ATZ, and BPA were 0.04 μg/L, 0.09 μg/L, 0.02 μg/L, and 0.03 μg/L, respectively. The FMB could also achieve early-warning of pollutants thanks to its ability of rapidity, high-frequency, and multiple-analyte detection. The FMB has significant implications as a multiplexable, portable, rapid, and quantitative detection platform for pollution accidents and water quality management to satisfy the increasing demands of alerting and protecting civilians.

Low-Loss High-Speed C-Band Fiber-Optic Switch Suitable for Quantum Signals

Quantum signals such as entangled photons are typically at the sub-photon level and, thus, require near noise-less and low-loss components for their manipulation and processing. A common signal-manipulation tool is a $2\,\,\times \,\,2$ switch, and many applications of quantum switches also require fast switching rates and input signals in the fiber-friendly 1550-nm band. Traditional optical switching technology does not simultaneously meet all the desired metrics for a quantum switch. We demonstrate a low-noise fiber-optic photonic switch based on cross phase modulation that is fast (sub-ns), low loss (<1 dB), and operates in the 1550-nm wavelength band.

Design and Analysis of Beam Steering Multicore Fiber Optical Switches

The design and performance characteristics of a beam steering optical switch for multicore fibers (MCFs) are reported. Port count, core count, transmission crosstalk, or a combination thereof can be optimized for the required application. Decreasing port separation or increasing the maximum steering angle both increase port count, whilst a higher core count or larger mode field diameter increase port capacity or port count, respectively, at the expense of greater intercore crosstalk. Potential losses from system misalignments and fiber fabrication variations in the core pitch are also estimated. A 50 port switch is possible for a 25 $\mu$ m core pitch 7 core hexagonal trench assisted MCF (TA-MCF) with a total mean statistical crosstalk on the central core of $-$ 25 dB after 1 km, assuming an operational wavelength of 1550 nm and maximum collimator actuator angle of 10 $^{\circ }$ . In contrast, a high capacity 25 $\mu$ m core pitch 61 core hexagonal TA-MCF can still offer up to a 5 port switch for the same level of crosstalk. For longer link distances, $-$ 25 dB crosstalk after 100 km (metro network) is achievable for a 50 port switch using a 35 $\mu$ m core pitch 7 core TA-MCF. Similar levels of crosstalk can be accomplished at 1000 km (core network) for a 41 port switch using a 25 $\mu$ m core pitch 7 core TA-MCF.

A Clinical Prototype Transrectal Diffuse Optical Tomography (TRDOT) System for In vivo Monitoring of Photothermal Therapy (PTT) of Focal Prostate Cancer.

We describe the rationale, design, fabrication and performance of a clinical transrectal diffuse optical tomography (TRDOT) system for in vivo monitoring of photothermal therapy (PTT) of localized prostate cancer. The system comprises a 32-channel fiberoptic-based, MRI-compatible transrectal probe connected to a computer-controlled instrument that includes laser diode sources, an optical fiber switch and photomultiplier tube detectors. Performance tests were performed in tissue-simulating phantoms and in ex vivo muscle tissue during PTT treatment. The safety and technical feasibility of in vivo transrectal use were tested in a canine prostate model and in a first-in-human study in a patient before PTT treatment. Limitations of the system are discussed, as well as further developments to translate it into planned clinical trials for monitoring the photocoagulation boundary in the prostate during PTT.

A novel dual-color total internal reflection fluorescence detecting platform using compact optical structure and silicon-based photodetector

A novel dual-color total internal reflection fluorescence detecting platform (DTP) was developed for the simultaneous detection of two fluorescence dyes. The DTP employed a simple and compact optical system and a Si-based photodetector SOP-1000 assembly to improve the optical efficiency and detection sensitivity. In the optical system, a single-multimode fiber optic coupler was applied for the transmission of two wavelength excitation lights and the collection and transmission of two wavelength fluorescence signals, and a fiber optical switch controlled two wavelength excited lights to alternatively enter into the combined tapered fiber optic probe and two wavelength fluorescence dyes were alternatively excited. The simultaneous and sensitive detection of two wavelength fluorescence signals was achieved by one photodetector SOP-1000 based on the time-resolved effect of the fiber optical switch. The DTP demonstrated its sensitivity of 50 fW light intensity, and the limit of detection of Cy5.5 and Pacific Blue dye (PB) were 0.05 nM and 2.1 nM, respectively. This miniaturized and integrated DTP with high sensitivity, simple optical structure, negligible cross-talk, and cost-effectiveness could be a potential alternative to the conventional dual-color fluorescence detecting systems. It could also be a powerful component of a μ-TAS system for highly sensitive dual-color fluorescence detection.

Development of dual-color total internal reflection fluorescence biosensor for simultaneous quantitation of two small molecules and their affinity constants with antibodies

A novel dual-color total internal reflection fluorescence biosensor (DTB) was successfully developed for the simultaneous detection of two small molecules based on a simple optical structure and the time resolved effect of fiber optic switch. The DTB employed a single-multi mode fiber optic coupler instead of a sophisticated confocal optical system for the transmission of two excitation lights and dual-color fluorescence, and a photodiode detector instead of photomultiplier for the simultaneous detection of dual-color fluorescence. The compact optical design of DTB improved its optical transmission efficiency and detection sensitivity because of no requirement of numerous optical separation elements and rigorous optical alignment. The DTB was applied for the simultaneous detection of 2,4-Bisphenol-A (BPA) and 2,4-Dichlorophenoxyacetic acid (2,4-D) using one bifunctional fiber optic bio-probe modified by two hapten-protein conjugates. When the mixture of Cy5.5 labeled anti-2,4-D antibody and Pacific Blue dye labeled anti-BPA antibody was introduced over the surface of the bio-probe, they bound with their respective hapten-protein conjugate immobilized onto the bio-probe. Based on the time-resolved effect of fiber optic switch, two fluorescence dyes were alternatively excited by 635 nm and 405 nm laser lights and simultaneously detected by one photodiode detector. Taking indirect competitive immunoassay principle, BPA and 2,4-D were simultaneously detected using the DTB with high sensitivity, accuracy, and rapidity. The quantitation of affinity constants between small molecules and their antibodies was also achieved based on the proposed theory. The DTB provides a flexible and powerful platform for simultaneously sensitive quantitation of multiple targets and the affinity constants of biomolecular interactions.