Jayakrishnan Chandrappan

Tagging module for lesion localization in capsule endoscopy

Capsule endoscopes are effective diagnostic tools for the gastro intestinal tract disorders at patients comfort. However the present capsule endoscopes lack efficient localization techniques to specify a pathological area that may require further diagnosis or treatment. This paper presents the development of a tagging module based novel method for the real-time localization of the site of interest. The tagging module consists of a bio compatible micro tag, compressed spring with a string latch and thermal igniter. The module can be integrated with the capsule endoscope and activated using an external trigger signal. On activation, the micro tag releases instantly and penetrates the mucosa layer of GI tract, region of interest. X-ray imaging is used to detect the location of micro tag embedded in GI tract wall. The radiopaque micro tags provide pre-operative valuable position information of the infected area to facilitate further clinical procedures.

Development of Optical Subassembly for Plastic Optical Fiber Transceiver in High-Speed Applications

A low-cost optical subassembly design for large core fiber transceiver is presented. The complete transceiver module is realized by assembling the low-cost optical subassembly directly on the transceiver functional printed circuit board. -7 dBm optical power output and 6 dB extinction ratio are achieved on transmitter by the vertical self-alignment and horizontal passive alignment at the transmitter. 190 m link distance is achieved at 2.5 Gb/s and 340 m link distance is achieved at 1.25 Gb/s for the plastic optic fiber (POF) transmitter with grade index plastic optical fiber. 145 m link distance is achieved at 2.5 Gb/s for the POF receiver.

Optical Coupling Methods for Cost-Effective Polymer Optical Fiber Communication

In this paper, we report cost-effective light coupling methods for polymer optical fiber (POF) communication. Here, we compare the various optical coupling schemes in detail. By optical simulations, we analyze the conventional light coupling schemes, namely the direct coupling, lens coupling, and lensed fiber coupling. The simulation studies reveal that a lensed fiber tip particularly at the receiver side improves the light coupling efficiency to a great extent. The optimized lensed POF design confers an 85% coupling efficiency. Lensed POFs are realized with two low-cost fabrication methods. The characterization of the lensed POF are carried out to evaluate the lensing properties and hence to optimize the fabrication process.

Design and Analysis of 3D Stacked Optoelectronics on Optical Printed Circuit Boards

In this study, a low-cost (with bare chips) and high (optical, electrical, and thermal) performance optoelectronic system with a data rate of 10Gbps is designed and analyzed. This system consists of a rigid printed circuit board (PCB) made of FR4 material with an optical polymer waveguide, a vertical cavity surface emitted laser (VCSEL), a driver chip, a 16:1 serializer, a photo-diode detector, a Trans-Impedance Amplifier (TIA), a 1:16 deserializer, and heat spreaders. The bare VCSEL, driver chip, and serializer chip are stacked with wire bonds and then solder jointed on one end of the optical polymer waveguide on the PCB via Cu posts. Similarly, the bare photo-diode detector, TIA chip, and deserializer chip are stacked with wire bonds and then solder jointed on the other end of the waveguide on the PCB via Cu posts. Because the devices in the 3D stacking system are made with different materials, the stresses due to the thermal expansion mismatch among various parts of the system are determined.

Design and Characterization of Taper Coupler for Effective Laser and Single-Mode Fiber Coupling With Large Tolerance

A new method of coupling the light from a laser diode (LD) to a single-mode fiber with large alignment tolerances and without using any coupling lens is presented. A pseudovertical tapered coupler on silicon substrate which has an input aperture of about 100 times the size of the laser waveguide cross section is designed. Results showed that the coupler relaxes the LD placement tolerance and eliminates the use of a coupling lens. The positional tolerance between the LD and taper coupler can be larger than +/- 5 mu m in the xy plane, and +/-1 deg in orientation.

Thermo-mechanical actuator-based miniature tagging module for localization in capsule endoscopy

Capsule endoscopy is a frontline medical diagnostic tool for the gastro intestinal tract disorders. During diagnosis, efficient localization techniques are essential to specify a pathological area that may require further diagnosis or treatment. This paper presents the development of a miniature tagging module that relies on a novel concept to label the region of interest and has the potential to integrate with a capsule endoscope. The tagging module is a compact thermo-mechanical actuator loaded with a biocompatible micro tag. A low power microheater attached to the module serves as the thermal igniter for the mechanical actuator. At optimum temperature, the actuator releases the micro tag instantly and penetrates the mucosa layer of a GI tract, region of interest. Ex vivo animal trials are conducted to verify the feasibility of the tagging module concept. X-ray imaging is used to detect the location of the micro tag embedded in the GI tract wall. The method is successful, and radiopaque micro tags can provide valuable pre-operative position information on the infected area to facilitate further clinical procedures.

A Pluggable Large Core Step Index Plastic Optical Fiber With Built-In Mode Conditioners for Gigabit Ultra Short Reach Networks

Large core step-index plastic optical fibers (SI-POF) are bandwidth limited due to their high modal dispersion and coupling loss at the receiver. To date, the large core SI-POF are typically deployed up to 150 Mb/s applications. This paper reports the transmission of 2.5 Gb/s on 980 μm core step-index plastic optical fiber with fiber-based mode conditioning elements that are part of the connector assembly. The built-in mode conditioners are tapered fiber tips that provide restricted mode launching at transmitter and mode filtering at the receiver side. The structures, at the tip of POF, are optimized by optical simulations and fabricated using laser fusion process. The connector assembly is realized by precisely encapsulating the mode conditioners with a metallic ferrule and positioned using optical grade epoxies. These plug-in modules are inserted to a typical SFP transceiver LC connector receptacle and characterized for gigabit rates.

Silicon micro heater based tagging module and the biocompatible packaging for capsule endoscope

Capsule endoscopes are widely used in gastro intestinal tract imaging. Current devices lack ways to precisely mark locations of interests during the image diagnose process. This paper presents a low-power micro heater module based on silicon technology, which can be integrated inside a capsule endoscope for precise localization. A custom polycarbonate capsule package is developed for both the tagging module and the capsule electronics. The complete system is then encapsulated with parylene thin film for biocompatibility purpose, which is analyzed in this study.

Optical alignment of dual-axis MEMS based scanning optical probe for Optical Coherence Tomography (OCT) application

In this paper we present the alignment process for a dual-axis electro-thermal actuated MEMS mirror, silicon optical bench (SiOB)-based probe for endoscopic optical coherence tomography (BOCT). The proposed optical design of the endoscope consists of the propagation of broadband low coherence light source from a 1310 nm laser source thru optical fiber, graded index (GRIN) lens, MEMS scanning mirror to the sample and back. The alignment approach undertaken consists of both passive and active elements. The passive element involves mounting and passively aligning the GRIN lens and MEMS scanning mirror onto trenches etched on separate SiOBs. This is followed by an active alignment of the two optical elements by first mounting each bench onto a five-axis stage rigged with a customized aluminum jig and a goniometer. An average double-pass coupling efficiency of 63.3% was achieved experimentally which was in line with optical simulation results. A fully functional probe was assembled and the cross-sectional images obtained are then presented within the paper. The difference in coupling efficiency resulting from the experiment/simulation and actual assembled probe is then reported and commented upon.

Performance Characterization Methods for Optoelectronic Circuit Boards

This paper illustrates the performance evaluation methods for bidirectional optoelectronic circuit boards (OECBs) operating at 10 Gb/s. A typical OECB consists of flip chip surface mount optical transceiver modules and polymer optical interconnects. The evaluation techniques include direct current and high-speed optical characterizations of individual components, subsystems, and interconnect. A methodical procedure to validate optical waveguide, vertical cavity surface emitting laser, photodiode, high-speed optical characterization of transmitter, receiver, and optical link is described.