1. A method for monitoring performance of an optical communication link, said method comprising:
obtaining an optical signal including a plurality of wavelength channels from said optical communication link;
passing said plurality of wavelength channels of said optical signal through a polarization beam splitter to separate two polarization components;
measuring a signal indicative of differences between said polarization components; and
determining whether there has been a failure of said optical communication link responsive to said signal indicative of said differences between said polarization components.
2. The method of claim 1 wherein obtaining said optical signal comprises:
tapping off said optical signal from said optical communication link as a monitor signal.
3. The method of claim 1 wherein said failure determining step comprises:
counting zero crossings of said signal indicative of said differences between said polarization components for a predetermined time interval.
4. Apparatus for monitoring performance of an optical communication link, said apparatus comprising:
a tap to obtain a monitor signal from said communication link;
a polarization beam splitter that isolates two polarization components of said monitor signal;
a differential amplifier that amplifies a difference of electronic signals derived from said two polarization components; and
a component responsive to an output of said differential amplifier to determine a failure of said optical communication link from zero crossings at said output.
5. The apparatus of claim 4 wherein zero-crossings in output of said differential amplifier indicate presence of signal on said optical communication link.
6. The apparatus of claim 4 wherein said monitor signal comprises multiple wavelengths carried by said optical communication link.
7. The apparatus of claim 4 wherein said component comprises a counter to count said crossings.
8. The apparatus of claim 4 wherein said component comprises an analog to digital converter to determine said failure digitally.
9. Apparatus for monitoring performance of an optical communication link, said apparatus comprising:
means for obtaining an optical signal including a plurality of wavelength channels from said optical communication link;
means for passing said plurality of wavelength channels of said optical signal through a polarization beam splitter to separate two polarization components;
means for measuring a signal indicative of differences between said polarization components; and
means for determining whether there has been a failure of said optical communication link responsive to said signal indicative of said differences between said polarization component.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An implantable pressure monitor comprising:
a substantially rigid chip including:
a proximal end and a distal end;
pressure sensors exposed on a first surface of the chip in a sensor region of the distal end;
signal processing circuitry receiving pressure-indicative signals from the sensors and producing pressure-indicative output signals; and
a chip electrical connector in the proximal end communicating the output signals;
a substantially rigid substrate that:
is spaced apart from the chip;
faces the first surface of the chip;
is connected to the chip electrical connector in the chip’s proximal end by a substrate electrical connector;
defines an aperture positioned over the sensor region of the chip’s distal end, thereby exposing the pressure sensors; and
covers the distal end of the chip except for the sensor region;
a flexible filler material located throughout space between the chip and the substrate except beneath the aperture, thereby leaving the pressure sensors exposed, such that (a) the flexible filler material connects the chip to the substrate, and (b) the distal end of the chip is connected to the substrate by only the flexible filler material;
a wire that:
extends from the substrate;
is electrically connected to the substrate electrical connector;
communicates the output signals; and
is not connected to the chip;
a biocompatible sheath that encapsulates the chip, substrate, filler, and wire, and is sufficiently flexible to transmit pressure exerted on the sheath exterior through the sheath; and
a pressure-transferring medium extending from the sheath, through the aperture, and to the pressure sensors, thereby transferring pressure exerted on the sheath exterior to the pressure sensors.
2. The implantable pressure monitor of claim 1, wherein the sheath has a curved shape to reduce or eliminate hydrodynamic forces.
3. The implantable pressure monitor of claim 1, wherein the substantially rigid substrate extends proximally from the chip to a proximal end which comprises an anchor.
4. The implantable pressure monitor of claim 3, wherein the anchor comprises a transversely extending flange that forms suture wings.
5. The implantable pressure monitor of claim 1, further comprising a holder that fixedly receives the chip and the substantially rigid substrate and extends proximally to a proximal end which comprises an anchor.
6. The implantable pressure monitor of claim 5, wherein the holder further comprises a distal end cap protecting the chip and the substantially rigid substrate.
7. The implantable pressure monitor of claim 1, wherein the flexible filler material comprises silicone.
8. The implantable pressure monitor of claim 1, wherein the flexible filler material holds the chip and the substrate together in a fixed relationship.
9. The implantable pressure monitor of claim 1, wherein the substantially rigid substrate extends distally from the chip to a distal end which comprises a barrier wall protecting a distal end of the chip.
10. The implantable pressure monitor of claim 9, wherein the barrier wall forms an end cap at the distal end of the chip.
11. The implantable pressure monitor of claim 10, wherein the barrier wall extends in a direction substantially perpendicular to a plane of the substrate and to a height such that a top of the barrier wall is at or above a top of the chip.
12. The implantable pressure monitor of claim 9, wherein the substantially rigid substrate further extends distally from the barrier wall to a tapered front portion.
13. The implantable pressure monitor of claim 1, wherein the sheath comprises a one-piece, seamless silicone covering.
14. The implantable pressure monitor of claim 13, wherein the flexible filler material comprises silicone.
15. The implantable pressure monitor of claim 1, wherein the substrate is sufficiently rigid such that it cannot be folded or rolled up.
16. The implantable pressure monitor of claim 1, wherein the substrate is sufficiently rigid to protect the pressure sensors from damage as a consequence of contact with a surgical instrument during implantation and from mechanical damage during use.
17. The implantable pressure monitor of claim 1, wherein the substrate is sufficiently rigid to avoid twisting of the chip due to turbulent blood flow.
18. The implantable pressure monitor of claim 1, wherein the substrate is rigid.
19. The implantable pressure monitor of claim 1, wherein the substrate is mechanically inflexible.