Conventional Optical Spectrum Analyzer Research Articles

Optical Fiber Coupler With a Hollow Core Fiber for Magnetic Fluid Detection

A new type of optical fiber coupler composed of a conventional solid core fiber and a hollow core fiber (HCF) is proposed. The hollow core of the HCF can be filled with various functional liquids and thus provides flexibility in tuning the guiding properties of photons. This enables the proposed coupler to be used as a versatile fiber sensing device. The experimental results revealed its sensitivity to be 73 000 nm/RIU. Compared with a vibrating sample magnetometer with a sensitivity of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> emu and accuracy of ± 1% in the magnetic sensing, the new fiber coupler was estimated to have a higher sensitivity of 2.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-10</sup> emu and an accuracy of ± 1.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> % under an optimal performance condition in a conventional optical spectrum analyzer.

Human Immunoglobulin Class G (IgG)) Antibody Detection With Photonic Crystal Fiber

Dye-free antibodies were identified in a less than 5-nL volume with a solid-core photonic crystal fiber (SC-PCF). The all-silica fiber contained micrometer-sized features with a 3- ${\mathbf {\mu }}$ m diameter core supported by a steering wheel-shaped lattice. These structures can be employed to monitor the presence of immunobased assays and susceptible secondary antigens specific to the detection application. A 0.8-m section of SC-PCF was filled with a 4.47-nL antibody sample and a LED light source in the 1300 $\text{-}$ 1700 nm range was employed. Although similar sensing configurations exist, the novelty of this investigation is the detection of this particular antibody. This experiment uniquely investigates the spectral characteristics of purified human immunoglobulin class G (IgG) (format-UNLB) in aqueous media. The absorption spectra for the monoclonal antibodies were collected with a conventional optical spectrum analyzer. The antibody solution exhibited two distinct absorption peaks, a water-linked absorption peak between 1400 and 1470 nm, with a maximum absorption power of 1.65 nW, and an antibody-linked absorption peak between 1485 and 1590 nm, with a maximum absorption power of 3.2 nW.

Wavelength-encoded tomography based on optical temporal Fourier transform

We propose and demonstrate a technique called wavelength-encoded tomography (WET) for non-invasive optical cross-sectional imaging, particularly beneficial in biological system. The WET utilizes time-lens to perform the optical Fourier transform, and the time-to-wavelength conversion generates a wavelength-encoded image of optical scattering from internal microstructures, analogous to the interferometery-based imaging such as optical coherence tomography. Optical Fourier transform, in principle, comes with twice as good axial resolution over the electrical Fourier transform, and will greatly simplify the digital signal processing after the data acquisition. As a proof-of-principle demonstration, a 150 -μm (ideally 36 μm) resolution is achieved based on a 7.5-nm bandwidth swept-pump, using a conventional optical spectrum analyzer. This approach can potentially achieve up to 100-MHz or even higher frame rate with some proven ultrafast spectrum analyzer. We believe that this technique is innovative towards the next-generation ultrafast optical tomographic imaging application.

Performance of parametric spectro-temporal analyzer (PASTA)

Parametric spectro-temporal analyzer (PASTA) is an entirely new wavelength resolving modality that focuses the spectral information on the temporal axis, enables ultrafast frame rate, and provides comparable resolution and sensitivity to the state-of-art optical spectrum analyzer (OSA). Generally, spectroscopy relies on the allocation of the spectrum onto the spatial or temporal domain, and the Czerny-Turner monochromator based conventional OSA realizes the spatial allocation by a dispersive grating, while the mechanical rotation limits its operation speed. On the other hand, the PASTA system performs the spectroscopy function by a time-lens focusing mechanism, which all-optically maps the spectral information on the temporal axis, and realizes the single-shot spectrum acquisition. Therefore, the PASTA system provides orders of magnitude improvement on the frame rate, as high as megahertz or even gigahertz in principle. In addition to the implementation of the PASTA system, in this paper, we will primarily discuss its performance, including the tradeoff between the frame rate and the wavelength range, factors that affect the wavelength resolution, the conversion efficiency, the power saturation and the polarization sensitivity. Detection bandwidth and high-order dispersion introduced limitations are also under investigation. All these analyses not only provide an overall guideline for the PASTA design, but also help future research in improving and optimizing this new spectrum resolving technology.

Optimization of Thermo-Optic Parameters for Temperature-Insensitive LPWG Refractometers

In this paper, we report numerically calculated results of testing a temperature-insensitive refractive sensor based on a planar-type long-period waveguide grating (LPWG). The LPWG consists of properly chosen polymer materials with an optimized thermo-optic coefficient for the core layer in a four-layer waveguide structure. The resonant wavelength shift below the spectral resolution of the conventional optical spectrum analyzer is obtained accurately over a temperature change of ±7.5°C even without any temperature control. The refractive index sensitivity of the proposed grating scheme is about 0.004 per resonant wavelength shift of 0.1 nm for an optimized thermo-optic coefficient.

Multi - channel Spectrum Analyzer for High Capacity Optical Transport Networks

A simple multi-channel spectrum analyzer using an InGaAs array sensor and a diffraction grating is proposed and developed for high-capacity optical transport networks. With the developed multichannel spectrum analyzer, we could measure signal power, wavelength, and optical signal-to-noise ratio of each channel for multi-channel optical signals with 100 GHz and 50 GHz channel spacing, simultaneously. We could measure each channel power and wavelength with a deviation of less than 0.2 dB and 0.063 nm, respectively. We have obtained optical signal-to-noise ratio with a deviation of less than 1.0 dB compared with conventional optical spectrum analyzer in the wide input power range between -42 dBm and -27 dBm per channel.