Configuration control of mode coupling errors

A rotation sensor capable of sensing rotation about an axis of a coiled optical fiber having a pair of principle birefringent axes including a fast axis and a slow axis, said sensing based on electromagnetic waves propagating in opposite directions in said coiled optical fiber to impinge on a photodetector with a phase relationship, said rotation sensor comprising:

• a source capable of supplying an emitted electromagnetic wave characterized by an autocorrelation relationship over relative retardation time having therein a succession of peak values each separated form any other peak value adjacent thereto in said succession by a corresponding retardation interval, said autocorrelation relationship, for at least a plurality of initial ones of said retardation intervals, having values during a fraction of each that are relatively smaller than those said peak values thereof correspondingly adjacent to such retardation intervals;
• a loop coupler having a pair of loop ports each with a pair of principal birefringent axes including a fast axis and a slow axis, and having at least one source port with a pair of principal birefringent axes including a fast axis and a slow axis, such that electromagnetic waves, occurring along said pair of principle birefringent axes of said source port, are substantially transmitted through a coupling region in said loop coupler primarily to be at least in part along corresponding ones of said pairs of principle birefringent axes of both said loop ports, and such that electromagnetic waves, occurring along said pair of principle birefringent axes of said loop ports, are substantially transmitted through said coupling region to be at least in part along corresponding ones of said pair of principle birefringent axes of said source port;
• a first coupling means for coupling said loop ports of said loop coupler to corresponding ends of said coiled optical fiber such that polarized electromagnetic waves, occurring along each axis of said pairs of principle birefringent axes of said loop ports, are substantially transmitted to said coiled optical fiber to result in electromagnetic waves propagating through said coiled optical fiber in opposite directions;
• a polarizer having first and second ports each with a corresponding pair of principle polarization axes such that polarized electromagnetic waves, occurring along a transmission axis of said pair of principle polarization axes of one of said first and second ports thereof, are substantially transmitted to result in polarized electromagnetic waves appearing along said transmission axis of that remaining one of said ports, and such that polarized electromagnetic waves, occurring along a blocking axis of said pair of principle polarization axes of one of said first and second ports thereof, are substantially blocked from being transmitted to that corresponding said blocking axis of that remaining one of said ports;
• a second coupling means coupling said first port of said polarizer to said source such that electromagnetic waves, emitted by said source, occur along at least said transmission principle polarization axis of said first port;
• and
• an optical path length determination means having a pair of principle birefringent axes, including a fast axis and a slow axis, and coupled to said second port of said polarizer such that polarized electromagnetic waves, occurring along at least one of said principle axes of said second port of said polarizer, are substantially transmitted primarily to being along a corresponding one of said pair of principle birefringent axes of said optical path length determination means, said optical path length determination means being also coupled to said source port of said loop coupler such that polarized electromagnetic waves, occurring along at least one of said principle birefringent axes of said optical path determination means, are substantially transmitted primarily to being along a corresponding one of said pair of principle birefringent axes of said source port, there being a pair of sets of electromagnetic wave transmission paths with each said set having each such path therein along a corresponding one of said principle polarization axes of said polarizer and with said electromagnetic wave transmission paths each (a) beginning from a corresponding wave coupling location within said second coupling means at which coupling of electromagnetic waves occurs between pairs of said paths having each pair member from a different said set, and (b) continuing along those said principle birefringent axes corresponding to one another in said optical path length determination means and said loop coupler to a corresponding wave coupling location within either of said loop coupler and said first coupling means at which coupling of electromagnetic waves also occurs between said pairs of said paths, said optical path length determination means being of a length such that polarized electromagnetic waves, propagating over pairs of said electromagnetic wave transmission paths containing a member from each said set to result in propagation time differences therebetween that are less than or equal to that delay equal to an initial four of said retardation intervals beginning from delay value zero, also have values for said time differences which differ substantially from delay values occurring at ends of any of said initial four of said retardation intervals.

A rotation sensor capable of sensing rotation about an axis of a coiled optical fiber having a pair of principle birefringent axes including a fast axis and a slow axis, said sensing based on electromagnetic waves propagating in opposite directions in said coiled optical fiber to impinge on a photodetector with a phase relationship, said rotation sensor comprising:

• a source capable of supplying an emitted electromagnetic wave characterized by an autocorrelation relationship over relative retardation time having therein a succession of peak values each separated from any other peak value adjacent thereto in said succession by a corresponding retardation interval, said autocorrelation relationship, for at least a plurality of initial ones of said retardation intervals, having values during a fraction of each that are relatively smaller than those said peak values thereof correspondingly adjacent to such retardation interval fractions;
• a polarizer having first and second ports each with a corresponding pair of principle polarization axes such that polarized electromagnetic waves, occurring along a transmission axis of said pair of principle polarization axes of one of said first and second ports thereof, are substantially transmitted to result in polarized electromagnetic waves appearing along said transmission axis of that remaining one of said ports, and such that polarized electromagnetic waves, occurring along a blocking axis of said pair of principle polarization axes of one of said first and second ports thereof, are substantially blocked from being transmitted to that corresponding said blocking axis of that remaining one of said ports;
• a source coupling means coupling said first port of said polarizer to said source such that electromagnetic waves, emitted by said source, occur along at least said transmission principle polarization axis of said first port;
• a loop coupler having a pair of loop ports each with a pair of principal birefringent axes including a fast axis and a slow axis, and having at least one source port with a pair of principal birefringent axes including a fast axis and a slow axis, such that electromagnetic waves, occurring along said pair of principle birefringent axes of said source port, are substantially transmitted through a coupling region in said loop coupler primarily to thereafter occur at least in part along corresponding ones of said pairs of principle birefringent axes of both said loop ports, and such that electromagnetic waves, occurring along said pair of principle birefringent axes of either of said loop ports, are substantially transmitted through said coupling region to thereafter occur at least in part along corresponding ones of said pair of principle birefringent axes of said source port;
• and
• a first coupling means for coupling said pair of loop ports of said loop coupler to corresponding ends of said coiled optical fiber such that polarized electromagnetic waves, occurring along each axis of said pairs of principle birefringent axes of said loop ports, are substantially transmitted to said coiled optical fiber to result in electromagnetic waves propagating through said coiled optical fiber in opposite directions, said first coupling means having a plurality of optical path components splices each resulting in a wave coupling location at which electromagnetic waves of opposite polarizations propagating along corresponding principle birefringent axes encounter coupling to an opposite such axis, including a first splice one side of which is provided by a said end of said coiled optical fiber and further including a second splice one side of which is provided by that remaining said end of said coiled optical fiber, and with each of said optical path components splices being separated along a corresponding separation optical path from said coupling region in said loop coupler by a corresponding length to result in a loop sides time difference between those time differences in propagation of electromagnetic waves of opposite polarizations along each member of a pair of said separation optical paths extending from opposite ones of said loop ports in said loop coupler such that said loop sides time differences for pairs of said separation optical paths, having values that are less than that delay equal to an initial four of said retardation intervals beginning from delay value zero, also have values which differ substantially from delay values occurring at ends of any of said initial four of said retardation intervals.

A rotation sensor capable of sensing rotation about an axis of a coiled optical fiber having a pair of principle birefringent axes, said sensing based on electromagnetic waves propagating in opposite directions in said coiled optical fiber to impinge on a photodetector with a phase relationship, said rotation sensor comprising:

• a source capable of supplying an emitted electromagnetic wave and having a characteristic coherence time;
• a loop coupler having a pair of loop ports and at least one source port such that electromagnetic waves, occurring at said source port, are substantially transmitted through a coupling region in said loop coupler to thereafter occur at least in part at both of said loop ports, and such that electromagnetic waves, occurring at either of said loop ports, are substantially transmitted through said coupling region to thereafter occur at least in part at said source port;
• a first coupling means for coupling said pair of loop ports of said loop coupler to corresponding ends of said coiled optical fiber such that electromagnetic waves, occurring at said loop ports, are substantially transmitted to said coiled optical fiber to result in electromagnetic waves propagating through said coiled optical fiber in opposite directions;
• a polarizer having first and second ports, each with a corresponding pair of principle polarization axes such that polarized electromagnetic waves, occurring along a transmission axis of said pair of principle polarization axes of one of said first and second ports thereof, are substantially transmitted to result in polarized electromagnetic waves appearing along said transmission axis of that remaining one of said ports, and such that polarized electromagnetic waves, occurring along a blocking axis of said pair of principle polarization axes of one of said first and second ports thereof, are substantially blocked from being transmitted to that corresponding said blocking axis of that remaining one of said ports, said second port of said polarizer being coupled to said source port of said loop coupler;
• and
• a second coupling means comprising a presplice means coupled to said source to receive electromagnetic waves, emitted by said source, for transmission to a splice end of a coupling optical fiber therein having a pair of principle birefringent axes, and further comprising a postsplice means coupled to said first port of said polarizer to receive electromagnetic waves at a splice end of a coupling optical fiber therein for transmission through an optical path length determination means therein to at least said transmission principle polarization axis of said polarizer first port, said postsplice means coupling optical fiber having a pair of principle birefringent axes, said optical path length determination means being of sufficient length such that polarized electromagnetic waves simultaneously introduced at one end thereof in alternate optical paths therethrough arrive at that end opposite with a time difference therebetween exceeding said source characteristic coherence time, said presplice means coupling optical fiber splice end being joined to said postsplice means coupling optical fiber splice end in a balanced splice through which electromagnetic waves can be transmitted in either direction and such that a said principle birefringent axis in one makes substantially equal angles with each of said principle birefringent axes of that one remaining.

A rotation sensor capable of sensing rotation bout an axis of a coiled optical fiber having a pair of principle birefringent axes, said sensing based on electromagnetic waves propagating in opposite directions in said coiled optical fiber to impinge on a photodetector with a phase relationship, said rotation sensor comprising:

• a source capable of supplying an emitted electromagnetic wave;
• a loop coupler having a pair of loop ports and at least one source port such that electromagnetic waves, occurring at said source port, are substantially transmitted through a coupling region in said loop coupler to thereafter occur at least in part at both of said loop ports, and such that electromagnetic waves, occurring at either of said loop ports, are substantially transmitted through said coupling region to thereafter occur at least in part at said source port;
• a first coupling means for coupling said pair of loop ports of said loop coupler to corresponding ends of said coiled optical fiber such that electromagnetic waves, occurring at said loop ports, are substantially transmitted to said coiled optical fiber to result in electromagnetic waves propagating through said coiled optical fiber in opposite directions;
• a polarizer having first and second ports each with a corresponding pair of principle polarization axes such that polarized electromagnetic waves, occurring along a transmission axis of said pair of principle polarization axes of one of said first and second ports thereof, are substantially transmitted to result in polarized electromagnetic waves appearing along said transmission axis of that remaining one of said ports, and such that polarized electromagnetic waves, occurring along a blocking axis of said pair of principle polarization axes of one of said first and second ports thereof, are substantially blocked form being transmitted to that corresponding said blocking axis of that remaining one of said ports;
• an optical path length determination means coupled between said second port of said polarizer and said source port of said loop coupler;
• and
• a second coupling means comprising a presplice means coupled to said source to receive electromagnetic waves, emitted by said source, for transmission without passage through any birefringence modulator to a splice end of a coupling optical fiber therein having a pair of principle birefringent axes, and further comprising a postsplice means coupled to said first port of said polarizer to receive electromagnetic waves at a splice end of a coupling optical fiber therein for transmission to at least said transmission principle polarization axis of said polarizer first port, said postsplice means coupling fiber having a pair of principle birefringent axes, said presplice means coupling optical fiber splice end being joined to said postsplice means coupling optical fiber splice end in a balanced splice through which electromagnetic waves can be transmitted in either direction and such that a said principle birefringent axis in one makes substantially equal angles with each of said principle birefringent axes of that one remaining, said optical path length determination means being of sufficient length such that polarized electromagnetic waves simultaneously introduced at said balanced splice in alternate optical paths in said postsplice means coupling optical fiber arrive at said loop coupler coupling region with a time difference therebetween having a value exceeding four times that time required for electromagnetic waves in said source to propagate one way over a distance along that path therein of greatest length over which such propagation can occur.

A rotation sensor capable of sensing rotation about an axis of a coiled, polarization-maintaining optical fiber, said sensing based on electromagnetic waves propagating in opposite directions in said coiled optical fiber to impinge on a photodetector with a phase relationship, said rotation sensor comprising:

• a source capable of supplying emitted electromagnetic waves having polarization components characterized by an autocorrelation relationship over relative retardation time having therein a succession of peak values each separated from any other peak value adjacent thereto in said succession by a corresponding retardation interval, said autocorrelation relationship, for at least a plurality of initial ones of said retardation intervals beginning from delay value zero, having values during a fraction of each that are relatively smaller than those said peak values thereof correspondingly adjacent to said retardation interval fractions;
• a polarizer means having a transmission axis and a blocking axis therein;
• a first coupling means coupling said coiled, polarization-maintaining optical fiber ends to said polarizer means, said first coupling means having at least one wave coupling location therein at which (a) electromagnetic waves propagate in opposite directions that also propagate in opposite directions in said coiled optical fiber, and at which (b) there is coupling between optical transmission paths into which are primarily directed electromagnetic waves emanating from said polarizer transmission and blocking axes, respectively;
• a second coupling means for coupling said polarizer means to said source and to said photo detector and comprising at least one segment of polarization-maintaining optical fiber, said second coupling means having at least one wave coupling location therein at which there is coupling between optical transmission paths into which are primarily directed electromagnetic waves polarization components emitted by said source, said wave coupling locations in said first coupling means and in said second coupling means having pairs of electromagnetic wave transmission paths between them in which each pair member passes through a different one of said polarizer means blocking and transmission axes such that polarization components of electromagnetic waves, propagating between pairs of such wave coupling locations to have propagation time differences in propagating thereover of values that are less than that delay equal to an initial four of said retardation intervals beginning from delay value zero, also have values for said time differences which differ substantially from delay values occurring at ends of said initial four of said retardation intervals.

A rotation sensor capable of sensing rotation about an axis of a coiled, polarization-maintaining optical fiber, said sensing based on electromagnetic waves propagating in opposite directions in said coiled optical fiber to impinge on a photodetector with a phase relationship, said rotation sensor comprising:

• a source capable of supplying emitted electromagnetic waves having polarization components characterized by an autocorrelation relationship over relative retardation time having therein a succession of peak values each separated from any other peak value adjacent thereto in said succession by a corresponding retardation interval, said autocorrelation relationship, for at least a plurality of initial ones of said retardation intervals beginning from delay value zero, having values during a fraction of each that are relatively smaller than those said peak values thereof correspondingly adjacent to said retardation interval fractions;
• an integrated optics chip having first, second and third ports such that electromagnetic waves introduced at said first port will result in electromagnetic waves appearing at said second and third ports after propagating over waveguides therein exhibiting a polarization characteristic in at least some location to establish therein a transmission axis and a blocking axis;
• a first coupling means coupling each of said coiled, polarization-maintaining optical fiber ends to a corresponding one of said integrated optics chip second and third ports, at least one of said integrated optics chip and said first coupling means having at least one wave coupling location therein at which (a) electromagnetic waves propagate in opposite directions that also propagate in opposite directions in said coiled optical fiber, and at which (b) there is coupling between optical transmission paths into which are primarily directed electromagnetic waves emanating from said transmission and blocking axes of that waveguide location exhibiting said polarization characteristic, respectively;
• and
• a second coupling means for coupling said integrated optics chip first port to said source, said second coupling means having at least one wave coupling location therein at which there is coupling between optical transmission paths into which are primarily directed electromagnetic waves polarization components emitted by said source, said wave coupling locations in said first coupling means and in said second coupling means having pairs of electromagnetic wave transmission paths between them in which each pair member passes through a different one of said waveguides blocking and transmission axes such that polarization components of electromagnetic waves, propagating between pairs of such wave coupling locations to have propagation time differences in propagating thereover of values that are less than that delay equal to an initial four of said retardation intervals beginning from delay value zero, also have values for said time differences which differ substantially from delay values occurring at ends of said initial four of said retardation intervals.

An interferometer capable of sensing phase differences between electromagnetic waves which have propagated in opposite directions in a coiled, polarization-maintaining optical fiber to impinge on a photodetector with a phase relationship, said rotation sensor comprising:

• a source capable of supplying emitted electromagnetic waves autocorrelation relationship over relative retardation time having therein a succession of peak values each separated from any other peak value adjacent thereto in said succession by a corresponding retardation interval, said autocorrelation relationship, for at least a plurality of initial ones of said retardation intervals beginning from delay value zero, having values during a fraction of each that are relatively smaller than those said peak values thereof correspondingly adjacent to said retardation interval fractions;
• a polarizer means having a transmission axis and a blocking axis therein;
• a first coupling means coupling said coiled, polarization-maintaining optical fiber ends to said polarizer means, said first coupling means having at least one wave coupling location therein at which (a) electromagnetic waves propagate in opposite directions that also propagate in opposite directions in said coiled optical fiber, and at which (b) there is coupling between optical transmission paths into which are primarily directed electromagnetic waves emanating from said polarizer transmission and blocking axes, respectively;
• a second coupling means for coupling said polarizer means to said source and to said photodetector and comprising at least one segment of polarization-maintaining optical fiber, said second coupling means having at least one wave coupling location therein at which there is coupling between optical transmission paths into which are primarily directed electromagnetic waves polarization components emitted by said source, said wave coupling locations in said first coupling means and in said second coupling means having pairs of electromagnetic wave transmission paths between them in which each pair member passes through a different one of said polarizer means blocking and transmission axes such that polarization components of electromagnetic waves, propagating between pairs of such wave coupling locations to have propagation time differences in propagating thereover of values that are less that delay equal to an initial four of said retardation intervals beginning from delay value zero, also have values for said time differences which differ substantially from delay values occurring at ends of said initial four of said retardation intervals.