This paper suggests an optical printed circuit board (OPCB) having new optical coupling structures, including a laser-drilled and under-filled structure (LD-UFS) and a vertical waveguide structure (VWS). The suggested OPCB has the features of high-speed data transmission as well as highly efficient optical coupling because it was fabricated with low-dielectric and transparent electrical PCB materials through a PCB compatible process. To evaluate and compare the optical and electrical performances of the suggested OPCB with those of other OPCBs, the various types of OPCBs were fabricated and measured. The optical coupling losses of the LD-UFS and the VWS were measured with excellent results of 9.8 and 7.8 dB, respectively, which are lower than that of the basic structure. The electrical 3-dB bandwidth of the OPCB was also evaluated up to more than 40 GHz.
We have demonstrated a refractive index sensor based on a fiber optic Fabry–Perot (FP) interferometer with an open air cavity fabricated using a one-step mechanical sawing technique. The sensor head consists of a short FP cavity near the fiber patch cord tip, which was assembled by joining a ceramic ferrule and a single-mode fiber together. Owing to the open air cavity in the sensor head, various liquid samples with different refractive index can fill in-line air cavity, which makes the device usable as a refractometer. Moreover, due to the sensor head encircled with the robust ceramic ferrule, the device is attractive for sensing measurement in harsh environments. The sensor was tested in different refractive index solutions. The experimental result shows that the attenuation peak wavelength of the sensor is shifted toward a shorter wavelength with increasing refractive index, and the refractive index sensitivity is ∼92.5 nm/refractive index unit (RIU) and 73.75 dB/RIU . The proposed sensor can be used as an in-line refractometer for many potential applications in the sensing field.
We demonstrate an optical planar waveguide sensor that can be used to measure the direction and intensity of
physical force. The interferometric structure, on which the proposed sensor is based, introduces an interference
pattern in wavelength. Its phase is shifted by the external force. On the other hand, since the cross-sectional effective
refractive index profile is asymmetric because of the core formed on one side of silica substrate, the phase shift
appears with respect to the direction of the external force against the surface. Therefore, we can measure the
direction and intensity of the applied force by monitoring the phase change.
We describe an ultra-thin and low-power optical interconnect module for mobile electronic devices such as mobile phones and notebooks. The module was fabricated by directly packaging optic and electronic components onto a thin and flexible optical printed circuit board having a size of 70×8×0.25 mm. The completed active module has features of thinness (0.5 mm), small size (7×5 mm), very low total power consumption (15.88 mW), and high data rate transmissions (2.5 Gbps).
We demonstrate a high speed fiber Bragg grating sensor array interrogation using 1.3 μm Fourier-domain modelocked
(FDML) wavelength-swept laser. The slope coefficients for measured relative wavelength difference and relative
time delay from the static strain are 1.02 pm/μstrain and 0.16 ns/μstrain, respectively. We demonstrate the dynamic
response of the FBG sensor array with 100 Hz modulation strain based on the FDML wavelength swept laser at 25.3 kHz
scanning rate. The FBG sensor interrogation system using FDML wavelength swept laser can be realized for the high
speed and high sensitivity monitoring systems.
A novel linearized interrogation method is presented for Fourier-domain mode locked (FDML) fiber Bragg grating
(FBG) sensor system. In the ultra high-speed regime over 10 kHz modulation, only sine wave is available to scan a
center wavelength of FDML wavelength-swept laser instead of conventional triangular wave. However, sine wave
modulation has been suffered an exaggerated nonlinear filter response in demodulating the time-encoded parameter into
the absolute wavelength. The linearized demodulation is demonstrated by the third order polynomial conversion of filter
between the time-encoded parameter and wavelength-encoded parameter based on the spectral information of
polarization maintaining fiber (PMF) Sagnac interferometer.
Novel wavelength-swept Raman laser is newly demonstrated to implement an arbitrary gain band for a swept-source optical coherence tomography (SS-OCT). Instead of conventional semiconductor optical amplifier, we adapt optical fiber Raman amplification, which can easily generate an instant femto-second optical gain at arbitrary wavelength region from 1.1 to 1.6 micrometer using a high-power optical pump power. We also experimentally demonstrate OCT images using the novel wavelength-swept Raman laser source.
Ultra-fast 31.3 kHz interrogation is newly demonstrated for fiber Bragg grating (FBG) sensor system using Fourierdomain
mode-locked (FDML) wavelength-swept laser. Higher speed interrogations are useful for the real-time
monitoring of dynamic sloshing pressure and strain.
Several technical problems have to be overcome before Optical Coherence Tomography (OCT) can be accepted among
the established endoscopic imaging modalities. Most of conventional Michelson-based OCT systems need to have two
separated paths of the sample and reference arms, which limits the flexibility of endoscopic probe. Recently, common-path
interferometer based OCT have been demonstrated to circumvent the mismatch problems of length, polarization,
and dispersion between the reference and sample arms, but the interferometric scanning methods have been realized with
time-domain PZT or spectral-domain CCD. In this work, we demonstrate a novel Fourier-domain common-path OCT
based on sweeping laser source, which shows superiority in the speed and robustness. Using a holey optical fiber with
low bending loss, a novel curled optical patch cord, like a curl cord of telephone, is also adapted for the convenient
access to the biological target at the flexible distance. The freedom to use an arbitrary length and wiring of the probe can
provide more flexibility for use in endoscopic OCT.
We demonstrate a novel implementation of spectral domain OCT by using a proposed sweeping detector at 1320 nm
wavelength range. A fiber pigtailed Fabry-Perot tunable filter is newly adapted to receive spectral interferometer
information using a photo-receiver instead of using charged couple detector arrays. In order to show a possibility of the
scheme in other view point, we have changed the position of the Fabry-Perot tunable filter of the interferometer. The
combination of a super luminescent LED and a semiconductor optical amplifier was used as an optical source. Its output
power is about 10 mW and the spectral bandwidth is about 60 nm. The filtered light after passing thorough the Fabry-
Perot tunable filter has 0.15 nm instantaneous spectral linewidth with 1.3 mW average output power. The system with an
axial resolution of 12 μm performed OCT imaging of a cornea of a rat eye proving potential about the application of the
proposed sweeping detector OCT.
We demonstrate the feasibility of OCT imaging for the investigation of samples, which are processed by the short pulse laser. The use of short pulse lasers in various material processing have provided the advantages such as a high peak power and a small heat affected zone over conventional methods based on mechanical treatment. However, due
to the improper application of the lasers, the unwanted surface or structural deformation of materials and the thermal damages around an irradiation spot can be caused. Thus, the real-time monitoring/evaluation of laser processing performance in-situ is needed to prevent the excessive deformation of the material and to determine optimal processing conditions. As a standard method to investigation of the material processing by using the lasers, the
scanning electron microscopy (SEM) or the transmission electron microscopy (TEM) observation of a physically cleaved surface is used although sample damages are given during the cleaving and polishing process. In this paper, we utilized the OCT advantages such as high resolution and non-invasive investigation to evaluate the laser processing performance. OCT images for the deformation monitoring of the ABS plastic present correlation with images obtained from conventional investigation methods. OCT images of the maxillary bone clearly show the difference in the pit formation of the biological sample at different irradiation conditions. We prove the potential of
OCT for the evaluation of laser-processed various samples. Integrating OCT system into a laser processing system, we can visualize the effect of laser-based treatments in clinical and industrial fields.
There have been several technologies to enable high resolution cross-sectional images of biological tissues in optical coherence tomography (OCT) method. Optical frequency comb (OFC) source has been proposed to overcome the crosstalk problem among the CCD detector pixels of the continuous spectrum of light source. Recently, a passive-type OFC is demonstrated simply placing a Fabry-Perot interferometer filter right after the broadband light source, but it shows a high loss of output light power and limited tenability of channel spacing of multi-wavelength. In this work, we experimentally demonstrate a spectral comparison of a novel multi-wavelength source based on a fiber Sagnac interferometer. The channel spacing is flexibly tuned by the effective length control of polarization-maintaining fiber (PMF). The uniform and stable multi-wavelength spectral distribution is also helpful to obtain the higher sensitivity from the lower exposure intensity source to get a better quality spectral OCT image.
Various techniques have been suggested to build a fiber ring laser using a fiber Bragg gratings (FBG) as a lasing wavelength selection filter. For most of FBG filter, a circulator has been used as a key component to convert the reflection characteristic of FBG to the transmission spectrum, but it has been hard to tune the spectral reflectance or transmittance of FBG intrinsically. In this research, a multi-wavelength fiber ring laser is proposed based on a novel switchable bandpass filter to show tunable multiple lasing spectra with high extinction. The proposed switchable bandpass filter consists of multiple FBG's incorporating Sagnac loop interferometer configuration. Transmission spectra of bandpass filter can be greatly varied for more than 20 dB as changing the phase of polarization controller in the Sagnac loop. We experimentally demonstrate the lasing wavelength is easily selected by the switchable FBG's at multiple spectral positions.
A novel erbium-doped fiber laser with high extinction ratio of more than ~60 dB based on a tunable bandpass filter is proposed and experimentally demonstrated. The proposed tunable filter consists of fiber Bragg gratings incorporating Sagnac loop interferometer configuration.
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