We demonstrate direct bandwidth measurement of multimode polymer waveguides based on an optical sampling technique. The pulse shape can be completely recovered after transmission due to the advantages of optical sampling technology in the field of ultrashort pulse measurement. A reduction in averaged bandwidth (Bandwidth-length products) from 241 GHz (27 GHz·m) to 180 GHz (20 GHz·m) of 11 cm-long straight waveguides is observed when using mode scramblers (MS) to fully stimulate the higher-order modes. The effects such as bending, crossing, and twisting of both the rigid and flexible waveguides on the bandwidth are also investigated. The proposed method is effective for measuring the bandwidth and dispersions of waveguides, fibers and optical devices with a short length for varies applications.
We demonstrate direct time-domain bandwidth measurement of 11 cm-long multimode polymer waveguides based on an optical sampling technique for the first time. The pulse shape can be recovered after propagating waveguides due to the advantages of large bandwidth (low time resolution) of optical sampling technology. A reduction in averaged bandwidth (bandwidth-length product) from 241 GHz (27 GHz·m) to 180 GHz (20 GHz·m) of straight waveguides is observed when using mode scramblers to fully stimulate the higher-order modes. The effects such as bending and crossing structure of the waveguides on the bandwidth are also investigated. The proposed method is effective for measuring the bandwidth and dispersion of meter and centimeter-long waveguides, fibers and optical devices
We demonstrate single-mode polymer waveguides and devices fabricated by using commercially available UV-curable epoxies and the mosquito method for on-board high-speed optical interconnects application. Both circular core singlemode waveguides operating at 1550 nm with a transmission loss of 0.79 dB/cm and waveguide based devices such as 3D directional coupler and mode (de)multiplexer have been designed and fabricated. The results imply that the proposed single-mode polymer waveguides and devices have good potential in high-density and high-speed on-board optical interconnects application.
This paper demonstrate a large-size directly inscribed optical waveguide for card-to-card optical interconnects applications. The waveguide was fabricated with commercially available UV-curable epoxies by combining use of a needle-type liquid micro-dispenser and a 3-axis robot stage known as the mosquito method. We designed and fabricated an “E” shaped waveguide device with 3 input/output ports and three connection routes with a length of about 21 cm, 21 cm, and 27 cm, respectively, to fit card-to-card connections of the optical backplane. The optical layout was designed to be scalable for conventional backplane sizes. Moreover, both the optical and geometrical parameters of the waveguides are designed to be compatible with commercial devices and can be terminated with MT connectors. The measurement results show good optical performance in insertion loss, crosstalk, misalignment tolerance, and good uniformity for all the 18 channels. The average insertion loss of the 27 cm-long channels is about 4.5 dB and the misalignment tolerance is larger than 20 μm for 3 dB loss penalty. The measured inter-channel waveguide crosstalk is lower than 42 dB. The waveguides also show excellent high-speed transmission performances with a NRZ signal at a data rate of 32 Gb/s. The experimental results imply that the large-size directly inscribed circular core polymer waveguide device is suitable for card-to-card optical interconnects applications and especially useful and versatile for the development of the porotype systems.
We present a newly developed high performance fiber optics sensor for quasi-static strain measurement. The sensor consists of a piece of π-phase shifted FBG for static strain sensing, and fiber Fabry-Perot interferometer for reference, interrogated by an improved sideband interrogation method with real-time feedback loops. Strain resolution of 0.12 nano-strain was achieved with sampling rate up to 1 kS/s in laboratory experiments. Compared with previous sensor systems, the proposed method shows great improvement in the sensing rate as well as the resolution.
We developed a novel optical coherent domain reflectometer (OCDR) technique with large measurement range by using of dual frequency modulation. The probe and local oscillator beams are frequency modulated independently, and the sensing position can be adjusted digitally via the time delay between the driving signals for the two modulators. Meanwhile, the frequency tuning spans of the two paths are different to enable heterodyne detection. In the demonstrational experiments, a spatial resolution of 3.9 m over a range of 24.6 km fiber was achieved with 35 MHz tunable range of the modulator, and the spatial resolution keeps a constant over the whole measurement range.
We reported an optical fiber based temperature sensor with mK-order resolution, wide temperature range and excellent long term stability. The sensor composes of a fiber Bragg grating (FBG) as the sensing element, an HCN gas cell for absolute frequency reference. A distributed feedback diode laser with current modulation is used as the light source. To overcome the frequency-sweep nonlinearity of the laser, an auxiliary Fabry-Perot interferometer with free spectrum range of 10 MHz is employed. A cross-correlation algorithm is employed to calculate the center frequency difference between the FBG and the gas cell. With the proposed configuration, a temperature resolution of 0.41 mK was demonstrated in experiment. To the best knowledge, this is the first time that an mK order temperature resolution has been achieved by optical fiber sensor.
We demonstrate confinement of light in a submicron-diameter silica core by adding a Bragg multilayer cladding.
Simulation results show that silica core Bragg fibers with Si/SiO2 multilayer claddings exhibit stronger mode
confinement than air cladding silica fiber. The optical properties of Bragg fiber taper can be fine tuned via controlling
taper diameter and multilayer structures. In experiment, TE01 mode-shaped spots with full-width at half-maximum
(FWHM) of 1.2 μm are observed for the first time to our knowledge in solid-core Bragg fibers. By adjusting the
refractive index of high index layer, HE11 mode-shaped spots with FWHM of 0.75 μm are generated by 1.1 μm-core
Bragg fiber tapers. The proposed devices will be good candidates as polarization selection and mode conversion devices for nano-optical applications.
We demonstrate the possibility of confining light in a submicron silica core by introducing a Bragg multilayer cladding.
1 μm-core Bragg tapers with mode field diameters about 1.1 μm for 850 nm wavelength are successfully fabricated by a
sputtering technique combining with tapering method using a traveling burner. Simulation of the mode intensity profiles
for both our devices and air cladding silica fibers are made by a beam propagation method. Bragg fiber tapers show
stronger confinement than silica glass tapers. The ultra-small core Bragg taper device will be a good candidate as the
mode coupler for nano-optical devices.
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