The majority of high-grade serous ovarian cancers is now believed to originate in the fallopian tubes. Therefore, current practices include the pathological examination of excised fallopian tubes. Detection of tumors in the fallopian tubes using current clinical approaches remains difficult but is of critical importance to achieve accurate staging and diagnosis. Here, we present an intraoperative imaging system for the detection of human fallopian tube lesions. The system is based on optical coherence tomography (OCT) to access subepithelial tissue architecture. To demonstrate that OCT could identify lesions, we analyzed 180 OCT volumes taken from five different ovarian lesions and from healthy fallopian tubes, and compared them to standard pathological review. We demonstrated that qualitative features could be matched to pathological conditions. We then determined the feasibility of intraluminal imaging of intact human fallopian tubes by building a dedicated endoscopic single-fiber OCT probe to access the mucosal layer inside freshly excised specimens from five patients undergoing prophylactic surgeries. The probe insertion into the lumen acquired images over the entire length of the tubes without damaging the mucosa, providing the first OCT images of intact human fallopian tubes.
Nonlinear microscopy has already shown its impact in biological research, namely in the fields of neurobiology, immunology, cancer research and embryology. Typically, these microscopes operate under free space propagation, using a dichroic mirror to separate the nonlinear signals from the excitation laser. While powerful such implementations are difficult to translate from the laboratory to a clinical setting where the environment is less controlled. Therefore, we propose an alignment-free all-fiber nonlinear microscopy system at 1550 nm based on double-clad fibers (DCF). As sectioning is performed through nonlinear effects, nonlinear microscopy does not require a detection pinhole, and. the DCF inner cladding can be used for efficient collection of nonlinear signals. The built system allows for multiplexing second harmonic generation (SHG) and two-photon excitation fluorescence (2PEF), collected from the inner cladding; and reflectance confocal microscopy (RCM), detected from the core acting as the confocal pinhole. Finally, an asymmetric double-clad fiber coupler (DCFC) is used to address efficiently both DCF channels. This all-fiber system is more compact and less sensitive to alignment, but requires carefully managing the transmission of the femtosecond pulse in the fiber. This is addressed using dispersion compensation fiber, pulse compression and solitonic propagation. Additionally, with a source centered at 1550 nm, we benefit from reduced sample scattering thus increasing the depth of field in comparison with systems operating at 800 nm. Overall we believe that the developed system could be transferred in clinics to enable in-vivo and in-situ imaging of human patient.
In this proceeding we demonstrate a system combining optical coherence tomography (OCT) and hyper-spectral imaging (HSI) into a single dual-clad fiber (DCF). Combining these modalities gives access to the sample morphology through OCT and to its molecular content through HSI. Both modalities have their illumination through the fiber core. The OCT is then collected through the core while the HSI is collected through the inner cladding of the DCF. A double-clad fiber coupler (DCFC) is used to address both channels separately. A scanning spectral filter was developed to successively inject narrow spectral bands of visible light into the fiber core and sweep across the entire visible spectrum. This allows for rapid HSI acquisition and high miniaturization potential.
This work demonstrates the combination of optical coherence tomography (OCT) and hyperspectral imaging (HSI) using a double-clad optical fiber coupler. The single-mode core of the fiber is used for OCT imaging, while the inner cladding of the double-clad fiber provides an efficient way to capture the reflectance spectrum of the sample. The combination of both methods enables three-dimensional acquisition of the sample morphology with OCT, enhanced with complementary molecular information contained in the hyperspectral image. The HSI data can be used to highlight the presence of specific molecules with characteristic absorption peaks or to produce true color images overlaid on the OCT volume for improved tissue identification by the clinician. Such a system could be implemented in a number of clinical endoscopic applications and could improve the current practice in tissue characterization, diagnosis, and surgical guidance.
We present a linear all-fiber device exhibiting the functionality of a circulator, albeit for multimode fibers. We define a pseudo-circulator as a linear three-port component that transfers most of a multimode light signal from Port 1 to Port 2, and from Port 2 to Port 3. Unlike a traditional circulator which depends on a nonlinear phenomenon to achieve a non-reciprocal behavior, our device is a linear component that seemingly breaks the principle of reciprocity by exploiting the variations of etendue of the multimode fibers in the coupler. The pseudo-circulator is implemented as a 2x2 asymmetric multimode fiber coupler, fabricated using the fusion-tapering technique. The coupler is asymmetric in its transverse fused section. The two multimode fibers differ in area, thus favoring the transfer of light from the smaller to the bigger fiber. The desired difference of area is obtained by tapering one of the fiber before the fusion process. Using this technique, we have successfully fabricated a pseudo-circulator surpassing in efficiency a 50/50 beam-splitter. In all the visible and near-IR spectrum, the transmission ratio exceeds 77% from Port 1 to Port 2, and 80% from Port 2 to Port 3. The excess loss is less than 0.5 dB, regardless of the entry port.
This proceedings shows the combination of Optical Coherence Tomography (OCT) and Hyper-Spectral Imaging
(HSI) using a double-clad optical fiber. The single mode core of the fiber is used to transmit OCT signals,
while the cladding, with its large collection area, provides an efficient way to capture the reflectance spectrum
of the sample. The combination of both methods enables three-dimensional acquisition of sample morphology
with OCT, enhanced by the molecular information contained in its hyper-spectral image. We believe that the
combination of these techniques could result in endoscopes with enhanced tissue identification capability.
There is a strong clinical need for an optical coherence tomography (OCT) system capable of delivering concurrent
coagulation light enabling image-guided dynamic laser marking for targeted collection of biopsies, as opposed to a
random sampling, to reduce false-negative findings. Here, we present a system based on double-clad fiber (DCF)
capable of delivering pulsed laser light through the inner cladding while performing OCT through the core. A previously
clinically validated commercial OCT system (NVisionVLE, Ninepoint Medical) was adapted to enable in vivo
esophageal image-guided dynamic laser marking. An optimized DCF coupler was implemented into the system to
couple both modalities into the DCF. A DCF-based rotary joint was used to couple light to the spinning DCF-based
catheter for helical scanning. DCF-based OCT catheters, providing a beam waist diameter of 62μm at a working distance
of 9.3mm, for use with a 17-mm diameter balloon sheath, were used for ex vivo imaging of a swine esophagus. Imaging
results using the DCF-based clinical system show an image quality comparable with a conventional system with minimal
crosstalk-induced artifacts. To further optimize DCF catheter optical design in order to achieve single-pulse marking, a
Zemax model of the DCF output and its validation are presented.
Scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) benefit clinical diagnostic imaging in
ophthalmology by enabling in vivo noninvasive en face and volumetric visualization of retinal structures, respectively.
Spectrally encoding methods enable confocal imaging through fiber optics and reduces system complexity. Previous
applications in ophthalmic imaging include spectrally encoded confocal scanning laser ophthalmoscopy (SECSLO) and
a combined SECSLO-OCT system for image guidance, tracking, and registration. However, spectrally encoded imaging
suffers from speckle noise because each spectrally encoded channel is effectively monochromatic. Here, we demonstrate
in vivo human retinal imaging using a swept source spectrally encoded scanning laser ophthalmoscope and OCT (SSSESLO-
OCT) at 1060 nm. SS-SESLO-OCT uses a shared 100 kHz Axsun swept source, shared scanner and imaging
optics, and are detected simultaneously on a shared, dual channel high-speed digitizer. SESLO illumination and
detection was performed using the single mode core and multimode inner cladding of a double clad fiber coupler,
respectively, to preserve lateral resolution while improving collection efficiency and reducing speckle contrast at the
expense of confocality. Concurrent en face SESLO and cross-sectional OCT images were acquired with 1376 x 500
pixels at 200 frames-per-second. Our system design is compact and uses a shared light source, imaging optics, and
digitizer, which reduces overall system complexity and ensures inherent co-registration between SESLO and OCT
FOVs. En face SESLO images acquired concurrent with OCT cross-sections enables lateral motion tracking and three-dimensional
volume registration with broad applications in multivolume OCT averaging, image mosaicking, and
intraoperative instrument tracking.
Pathological evaluation of the fallopian tubes is an important diagnostic result but tumors can be missed using routine approaches. As the majority of high-grade serous ovarian cancers are now believed to originate in the fallopian tubes, pathological examination should include in a thorough examination of the excised ovaries and fallopian tubes. We present an dedicated imaging system for diagnostic exploration of human fallopian tubes. This system is based on optical coherence tomography (OCT), a laser imaging modality giving access to sub- epithelial tissue architecture. This system produces cross-sectional images up to 3 mm in depth, with a lateral resolution of ≈15μm and an axial resolution of ≈12μm. An endoscopic single fiber probe was developed to fit in a human fallopian tube. This 1.2 mm probe produces 3D volume data of the entire inner tube within a few minutes. To demonstrate the clinical potential of OCT for lesion identification, we studied 5 different ovarian lesions and healthy fallopian tubes. We imaged 52 paraffin-embedded human surgical specimens with a benchtop system and compared these images with histology slides. We also imaged and compared healthy oviducts from 3 animal models to find one resembling the human anatomy and to develop a functional ex vivo imaging procedure with the endoscopic probe. We also present an update on an ongoing clinical pilot study on women undergoing prophylactic or diagnostic surgery in which we image ex vivo fallopian tubes with the endoscopic probe.
In this paper we propose and demonstrate two forms of a device for sensing cladding modes efficiently. The cladding modes, generated by an untilted and tilted fibre Bragg grating (TFBG) written in SMF28 fibre are captured by splicing it to an in-line double-clad fibre coupler (DCFC). A comaprison is made of the capture efficiency of the cladding modes in two configurations; one in which the TFBG is taper spliced to the DCF, or in the other in which an FBG in an SMF28 is etched down to match the outer core of the DCF. In both cases the cladding modes are captured efficiently, but with significantly improved results for the former configuration. We demonstrate surrounding refractive index sensing using a new signal analysis scheme based on the extinction of each cladding mode resolved over a bandwidth of over ~60nm. This robust device has the advantage of faithfully transmitting the cladding modes over a long distance and is therefore suitable for remote sensing over long distances. The sensitivity of the device is discussed. This device may be used in a variety of applications such as for bend, strain, temperature and surrounding refractive index sensing.
We report here the successful realization of 25 millions wavelengths per second using an SOA based PL around 1565
nm at a 75 MHz repetition rate. The laser is simply composed of an SOA, a CFBG (10 ps/nm) with a 100 nm bandwidth,
an optical circulator, an EOM (intensity modulator), and an output coupler (20%). Pulse duration is around 45 ps and
OSNR of the pulse is around 35 dB at 1565 nm without sweeping. Tunable dispersion compensating module (TDCM)
was used to compress the chirped pulse output and 10 ps pulse duration was obtained at 1548 nm. Finally 25 megawavelengths
per second was realized with under 3 pulses per wavelength and 1024 discrete wavelengths. Linear k-space
sweeping function was enabled in the swept-source OCT (SS-OCT) system through graphical user interface (GUI).
The origin and the behavior of the birefringence of solid-core
air-silica microstructured fibers is described with
the help of a simple approximate model. The first two modes of three different types of fibers are studied.
Numerical results, obtained from both finite element and boundary integral methods calculations, are presented
to support the validity of the model and to delineate its limits.
We use the method of moments to calculate the propagation of an arbitrarily shaped pulse in a nonlinear
dispersive fiber. By assuming that the pulse is linearly chirped, we are able to determine analytically the
evolution of the second order moments (representing the duration, bandwidth and chirp of the pulse) along
propagation regardless of the initial pulse shape. The evolution of the moments is given by an implicit equation
and several invariants. These invariants allow an easy estimation of the different pulse parameters. The linear
chirp approximation implies that the arbitrary pulse shape remains invariant along propagation but allows to
calculate the propagation in both dispersion regimes from the same solution. The solution show an oscillatory
behavior in the anomalous dispersion regime and a monotonic behavior in the normal dispersion regime. In both
regimes the calculations are compared to numerical split-step simulations and are shown to agree for propagation
over many dispersion and nonlinear lengths.
While this method describes well the evolution of the pulse duration, bandwidth and chirp, we need to proceed
differently to find the evolution of the pulse shape. From these propagation equations for the moments, we
derive an approximate implicit solution describing the propagation of a Gaussian pulse in the normal dispersion
regime. This approximate solution describes the pulse shaping toward a parabola that the pulse undergoes
along propagation. A good agreement is found between the pulse obtained from numerically solving the implicit
equation and the split-step propagation of the same pulse. Numerically solving the implicit analytical function
describing the pulse is much faster than using purely numerical simulations, which becomes time consuming for
highly chirped pulses with large bandwidths over long propagation distances. These and other results suggest
that pulse shaping along propagation is only adequately modeled by implicit functions.
In this paper, we propose a solution for simple, fast and easily controllable way of tuning silicon gratings using Micro
Electro Mechanical Systems (MEMS) to deform the grating itself. Basically the idea is to deform mechanically a silicon
grating using electrostatic actuators, enabling pitch tuning over a large proportion (more than 50% is easily achievable
with our approach). Moreover we can change the spacing of individual layers within the grating. A theoretical analysis
and numerical simulations are presented and a first prototype is fabricated. Bragg gratings, springs and actuators are
realized by silicon micro/nano machining on a silicon platform enabling full integration and passive alignment of all
optical components. Applications range from ultra-sensitive displacement sensors, to telecommunications and biology.
The Raman gain spectrum of Phosphorous-doped optical fibers (PDF) is known to exhibit, in addition to the pure silica response, a strong 40 THz frequency-shifted Stokes peak relative to the pump. This large shift reduces the number of cascades required in Raman lasers using nested cavities. We report a measurement of the Raman gain coefficient for a PDF. Our measurement scheme has the advantage of requiring only a pump source and no signal. We developed a model taking into account both contributions from spontaneous and stimulated Raman scattering. Raman spectra gathered at several pump powers are fitted against this enhanced theoretical model. The experimental values of the Raman gain coefficient obtained are in agreement with published results.
For the last decade, recirculating loops have been a useful tool in the research and development of long haul transmission links. A loop experiment can emulate the transmission of an optical signal over thousands of kilometers by using a relatively short link of a few hundred kilometers and recirculating the signal several times. Although recirculating loops accurately replicate most physical effects encountered in point-to-point links (loss, noise, chromatic dispersion, nonlinear effects, etc), the statistics of polarization effects (polarization mode dispersion (PMD) and polarization-dependent loss (PDL)) may not be properly emulated. In an optical link, PDL can induce statistical fluctuations of the optical signal-to-noise ratio (OSNR) and consequently of the bit-error-rate (BER). Due to environmental changes, the effects of PDL vary stochastically in time. The periodic nature of fiber loop may artificially produce an unrealistic PDL distribution and the statistical distribution of PDL effect may be significantly different from that in a installed link. We report the analysis and observation of a power oscillation effect caused by PDL due to the periodic nature of the polarization evolution in a recirculating loop. The oscillation is expected to affect the OSNR and consequently the BER as a function of recirculation.
Quantum cryptography, or more specifically, quantum key distribution (QKD), has attracted a lot of attention in the recent years with the discovery that it can provide absolute secrecy for communications. We propose a new architecture for implementing a fiber-based network of quantum key distribution using optical wavelength division multiplexing in the fiber. We discuss the advantages over previous proposals and we report experimental work demonstrating the feasibility of the proposed architecture.
Maker fringes measurements performed with hemispherical lenses pressed against a planar sample permit the propagation of light at very high internal propagation angle, and therefore the observation of many more fringes. The thickness of the active nonlinear region can be determined with accuracy. Results from optical measurements are compared to what is predicted by a charge migration model and by observed currents to the electrodes during poling. This comparison is relevant to the identification of the origin of second-order nonlinearities in silica glasses.
Potential application of polymers containing ferrocene as their backbone compound in fiber optic gas sensors are discussed. The refractive indices of these polymers are comparable to silica glass and vary substantially upon exposure to certain gases. The variation in the refractive index of thin films of a ferrocene-based polymer known as methyl-phenyl-silane ferrocenylene polymer upon exposure to ammonia, nitrous oxide, nitric oxide, nitrogen, and oxygen is examined. The structure and operation of tapered optical fiber gas sensors fabricated with the aforementioned polymer are explained. Also covered are the sensitivity and reaction times of two different sensors to ammonia and nitrogen.
Summarized are two project areas: First, the development of a quantitative structure property relationship for analyzing thermal decomposition differential scanning calorimetry data of electro-optic dyes is presented. The QSPR relationship suggest that thermal decomposition can be effectively correlated with structure by considering the kinds of atoms, their hybridization, and their nearest neighbor bonded atoms. Second, the simple preparation of clad plastic optical fibers (POF) is discussed with the intention of use for nonlinear optical applications. We discuss preparation techniques for single core and multiple core POF, and present some recent data on index profiles and the optimization of thermal stability in acrylate-based POF structures.
A technique to find the steady-wave solutions in slab waveguides with or without Kerr nonlinearities is presented. This approach is based on the use of space-phase diagrams. It can simplify the resolution and the interpretation of linear problems, as well as provide a way to get the dispersion relation and power dependence of nonlinear waveguides. The technique is applied to a variety of three-layer waveguides exhibiting Kerr nonlinearities. The power dependence of the effective index is computed for all of these waveguides.