Optically Coupled Cochlear Implant Systems and Methods

Abstract

An output assembly is sized for placement in the middle and inner ear, such that removal of bone can be decreased. The output assembly may comprise at least one photo detector, a demultiplexer and an electrode array sized to pass through an incision in the eardrum. An input transducer assembly is configured to transmit a multiplexed optical signal to the output assembly. The input assembly can be configured to transmit the multiplexed optical signal through the eardrum, such that tissue removal can be decreased and the device can be placed without removal of bone, for example. The multiplexed optical signal may comprise a pulse width modulated signal so as to decrease the effect of non-linearities of the light source and light detector and provide quality sound to the user.

What is claimed is: 
     
         1 . A method of stimulating tissue, the method comprising:
 transmitting a multiplexed optical signal to stimulate the tissue.   
     
     
         2 . A method of transmitting a sound to a cochlea of a user, the user having a tissue, the method comprising:
 transmitting a multiplexed optical signal through the tissue of the user such that the user hears the sound in response to the multiplexed optical signal transmitted through the tissue.   
     
     
         3 . The method of  claim 2  wherein the tissue comprises tissue of an eardrum. 
     
     
         4 . The method of  claim 2  wherein the multiplexed optical signal is transmitted to an optical structure supported with the middle ear, the optical structure configured to separate wavelengths of the multiplexed signal to stimulate the cochlea. 
     
     
         5 . The method of  claim 4  wherein the said optical structure is affixed to the middle ear. 
     
     
         6 . The method of  claim 4  wherein the said optical structure is sized to pass through an incision in the eardrum for placement in the middle ear cavity. 
     
     
         7 . The method of  claim 4  wherein the optical structure comprises at least one of an optical filter, an optical fiber, a grating, an etalon, a plurality of optical fibers, a waveguide, a plurality of waveguides, a mirror or a prism. 
     
     
         8 . The method of  claim 4  wherein the multiplexed optical signal comprises a plurality of channels, each channel of the plurality corresponding to at least one frequency of the sound. 
     
     
         9 . The method of  claim 8  wherein the plurality of channels corresponds to at least about sixteen channels and said at least one frequency corresponds to at least about sixteen frequencies. 
     
     
         10 . The method of  claim 8  wherein the multiplexed optical signal is transmitted through the eardrum with a plurality of light sources, each light source configured to transmit a light signal corresponding to said channel of the plurality such that said light source corresponds to said at least one frequency of sound. 
     
     
         11 . The method of  claim 10  wherein the plurality of light sources comprises at least three light sources and wherein each of the at least three light sources is configured to emit separate wavelengths of light. 
     
     
         12 . The method of  claim 8  wherein each of the plurality of channels corresponds to a pair of electrodes and wherein a first current travels between said pair of electrodes in response to a first width modulated light pulse and a second current travels between said pair of electrodes in response to a second width modulated light pulse, the first current opposite the second current, the first current opposite the second current, the first current having a first amount corresponding to a first width of the first pulse and the second current having a second amount corresponding to a second width the second pulse, and wherein the width of the first pulse corresponds to the width of the second pulse so as to inhibit rectification and balance charge transfer between the first electrode and the second electrode. 
     
     
         13 . The method of  claim 12  wherein the first light pulse comprises a first wavelength of light coupled to a first detector and wherein the second light pulse comprises a second wavelength of light coupled to a second detector. 
     
     
         14 . The method of  claim 2  wherein the multiplexed optical signal is transmitted through the eardrum of the user to at least one photodetector, the at least one photodetector affixed to the middle ear and coupled to an electrode array positioned at least partially within the cochlea. 
     
     
         15 . The method of  claim 14  wherein the at least one photodetector and at least one electrode array are sized to pass through an incision in the eardrum. 
     
     
         16 . The method of  claim 14  wherein the multiplexed optical signal comprises a wavelength multiplexed optical signal, the wavelength multiplexed optical signal comprising a plurality of wavelengths such that each wavelength corresponds to an electrode of the array. 
     
     
         17 . The method of  claim 16  wherein each wavelength of the plurality corresponds to an electrode of the array. 
     
     
         18 . The method of  claim 16  wherein the at least one photodetector comprises a plurality of photodetectors, each photodetector of the plurality coupled to a corresponding electrode of the array and a corresponding wavelength of the plurality such that the tissue stimulating current is passed through the electrode in response to the tissue stimulating wavelength. 
     
     
         19 . The method of  claim 18  wherein further comprising an optical structure positioned in the middle ear of the user to separate the wavelengths to correspond with each detector, and such that each separated wavelength corresponding to each detector is transmitted to said each detector based on the wavelength. 
     
     
         20 . The method of  claim 18  further comprising a plurality of optical filters positioned in the middle ear of the user and wherein the wavelengths are separated with the optical filters, each optical filter positioned over one detector and configured to pass the wavelengths corresponding to the electrode coupled to said one detector. 
     
     
         21 . The method of  claim 18  wherein further comprising a grating configured to select the wavelengths of each detector to corresponding to each electrode. 
     
     
         22 . The method of  claim 14  wherein the multiplexed optical signal comprises a time division multiplexed signal. 
     
     
         23 . The method of  claim 22  wherein the time division multiplexed signal comprises the plurality of time-slots, each time slot of the plurality corresponding to an electrode of the array. 
     
     
         24 . The method of  claim 23  wherein the time division multiplexed signal comprises the plurality of time slots and a clock signal and wherein circuitry is coupled to the at least one photodetector and the electrode array to receive the clock signal and divide the time division multiplexed signal among the electrodes of the array such that each time slot corresponds to the electrode of the array. 
     
     
         25 . The method of  claim 24  wherein each time slot corresponds to at least one frequency of the sound such that current is passed through each electrode in response to a portion of the multiplexed signal corresponding to the time slot. 
     
     
         26 . The method of  claim 25  the time division multiplexed signal is pulse width modulated such that each timeslot of the plurality comprises a pulse of light having a duration that corresponds to current through the electrode corresponding to said timeslot. 
     
     
         27 . The method of  claim 2  wherein the multiplexed optical signal is transmitted to at least one optical fiber extending into the cochlea. 
     
     
         28 . The method of  claim 27  wherein the at least one optical fiber is sized to pass through an incision in the middle ear. 
     
     
         29 . The method of  claim 27  wherein the at least one optical fiber comprises a plurality of optical fibers extending into the cochlea, each fiber corresponding to at least one frequency of the sound. 
     
     
         30 . The method of  claim 27  wherein each fiber is configured to stimulate the cochlea at a predetermined location of the cochlea corresponding to a corresponding range of frequencies in response to the at least one frequency of the sound. 
     
     
         31 . The method of  claim 2  wherein the multiplexed optical signal is transmitted through at least one of an opening or a window in the eardrum. 
     
     
         32 . The method of  claim 2  wherein the electrode array, the at least one photodetector, and the demultiplexer comprise substantially non-magnetic materials configured for MRI imaging when implanted in the user. 
     
     
         33 . The method of  claim 2  wherein the sound comprises a phase and wherein the optical signal comprises width modulated light pulses transmitted with a frequency of at least about 10 kHz and wherein each light pulse generates an electrical current within the cochlea such that the cochlea demodulates the light pulses and the phase of the sound is maintained. 
     
     
         34 . The method of  claim 33  wherein the width modulated light pulses comprises a series of width modulated pulses for each channel and wherein the series of width modulated pulses of said each channel comprises a frequency of at least about 10 kHz to maintain the phase of the sound when the user hears the sound. 
     
     
         35 . The method of  claim 34  wherein the frequency of said each series comprises at least about 20 kHz to maintain the phase of the sound when the user hears the sound. 
     
     
         36 . The method of  claim 35  wherein the plurality of channels comprises at least about eight channels and the frequency of the width modulated light pulses comprises at least about 160 kHz. 
     
     
         37 . The method of  claim 34  wherein the pulses of the series of width modulated pulses of each channel are combined to form a sequence of packet of pulses, each packet comprising one pulse from each series. 
     
     
         38 . The method of  claim 2  wherein the at least one photodetector is positioned in the middle ear cavity so as to receive the multiplexed optical signal through a posterior portion of the eardrum. 
     
     
         39 . A device to stimulate tissue, the device comprising:
 means for generating a multiplexed optical signal; and means for stimulating tissue in response to the optical signal.