1. A pressure sensor employing a MEMS resonator, comprising:
a MEMS resonator;
a sweeping unit which sweeps a frequency of an excitation signal in a predetermined direction of sweeping, over a predetermined frequency range including a resonance frequency f0 of a vibrator in the MEMS resonator, while outputting the excitation signal to the MEMS resonator;
an integrating unit which inputs a vibrating-state information signal as a characteristic amount indicative of a vibrating state of the vibrator from the MEMS resonator while the sweeping unit sweeps the frequency, integrates a plurality of the vibrating-state information signals at different frequencies of the excitation signal, and outputs the integrated value; and
a conversion unit which determines a pressure acting on the MEMS resonator, based on the integrated value.
2. The pressure sensor according to claim 1, wherein
the integrating unit determines the integrated value, by integrating at least two vibrating-state information signals including a vibrating-state information signal of when the excitation signal has a frequency earlier than the resonance frequency f0 in the direction of sweeping, and a vibrating-state information signal of when the excitation signal has a frequency later than the resonance frequency f0 in the direction of sweeping.
3. The pressure sensor according to claim 2, wherein
the MEMS resonator comprises a capacitance-type MEMS resonator, and
the sweeping unit performs the sweeping in such a direction that the frequency of the excitation signal is gradually lowered, from a sweeping starting frequency f1 which is a frequency equal to or higher than the resonance frequency f0, to a sweeping completion frequency f2 which is a frequency lower than the resonance frequency f0.
4. The pressure sensor according to claim 3, wherein
the vibrator in the capacitance-type MEMS resonator is surrounded by an ambient atmosphere at a pressure equal to the pressure acting on the MEMS resonator, and
the conversion unit determines a Q factor of the MEMS resonator based on the integrated value and determines the pressure based on the determined Q factor.
5. The pressure sensor according to claim 3, wherein
the capacitance-type MEMS resonator includes:
a vibrator;
an electrode disposed in such a way as to interpose a gap between the electrode and the vibrator; and
a mechanism which changes a size of the gap according to the magnitude of the pressure acting on the capacitance-type MEMS resonator, and
the conversion unit determines the size of the gap based on the integrated value and determines the pressure based on the determined size of the gap.
6. The pressure sensor according to claim 2, wherein
the vibrating-state information signal comprises a signal including information about a vibration amplitude of the vibrator.
7. The pressure sensor according to claim 2, wherein
the vibrating-state information signal comprises a signal including information about a vibrating speed of the vibrator.
8. The pressure sensor according to claim 2, wherein
the vibrating-state information signal comprises a signal including information about an angle of flexure in the vibrator along with vibrating motion of the vibrator.
9. The pressure sensor according to claim 3, wherein
an absolute value of the difference between the sweeping starting frequency f1 and the sweeping completion frequency f2 is preliminarily determined, based on the product of a temperature characteristic of the elastic modulus of the vibrator and a temperature changing range expected in a pressure-sensor-use environment.
10. The pressure sensor according to claim 2, wherein
the MEMS resonator comprises a non-capacitance-type MEMS resonator, and
the sweeping unit performs the sweeping in such a direction that the frequency of the excitation signal is gradually heightened, from a sweeping starting frequency f1 which is a frequency equal to or lower than the resonance frequency f0, to a sweeping completion frequency f2 which is a frequency higher than the resonance frequency f0.
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 optical fibre for coupling to an optical source, the optical fibre comprising:
a) a core for receiving light directed from said optical source along an optical axis; wherein said core is expanded near one end of said optical fibre, the portion of the core which is expanded having a diameter larger than other portions of the core that are not expanded; and
b) a tip portion on said end of said optical fibre, wherein said tip portion further comprises an endmost face, said endmost face being non-perpendicular to said optical axis.
2. The optical fibre of claim 1, wherein said tip portion further comprises a lens such that said light transmitted from said optical source to said optical fibre goes through said lens.
3. The optical fibre of claim 2, wherein said lens is formed on an area overlapping with at least a part of said endmost face.
4. The optical fibre of claim 1, wherein said tip portion further comprises at least two side portions, each said side portion further comprising a surface extending from an outer periphery of said optical fibre toward said endmost face of said tip portion.
5. The optical fibre of claim 4, wherein said surface of each said side portion has an edge aligned with said endmost face of said tip portion, whereby said edges of said side portions contact said endmost face.
6. The optical fibre of claim 5, wherein said surfaces of said side portions are symmetrical about said endmost face of said tip portion and said tip portion is in a substantially wedge shape.
7. The optical fibre of claim 6, wherein said tip portion further comprises a first chamfer portion configured at a first end of said wedge.
8. The optical fibre of claim 7, wherein said tip portion further comprises a second chamfer portion configured at a second end of said wedge opposite to said first end.
9. The optical fibre of claim 1, wherein said endmost face of said tip portion further comprises an uneven surface.
10. The optical fibre of claim 1, wherein said diameter of said optical fibre is 125 \u03bcm.
11. The optical fibre of claim 1, wherein said optical fibre is a single mode optical fibre.
12. The optical fibre of claim 1, wherein an angle between a normal of said endmost face and said optical axis is approximately 6 degrees.
13. The optical fibre of claim 1, wherein said core end portion has a taper shape from said end of said optical fibre to said core.
14. A coupling system, comprising:
a) an optical device for generating a light signal; and
b) an optical fibre coupled to said optical device, wherein said optical fibre further comprises:
i) a core for receiving light directed from said optical source along an optical axis; wherein said core is expanded near one end of said optical fibre, said expanded core having a diameter larger than other portions of the core that are not expanded; and
ii) a tip portion on said end of said optical fibre, wherein said tip portion further comprises an endmost face, said endmost face being non-perpendicular to said optical axis.
15. The coupling system of claim 14, wherein said optical device is a laser semiconductor chip.
16. A method of fabricating a coupling device for an optical fibre for coupling to an optical source, comprising the steps of:
a) expanding a portion of a core in said optical fibre near one end of said optical fibre; said core capable of receiving light directed from said optical source along an optical axis; said expanded core after said expanding having a diameter larger than other portions of the core that are not expanded; and
b) forming a tip portion on said end of said optical fibre, wherein said tip portion further comprises an endmost face, said endmost face being non-perpendicular to said optical axis.
17. The method of claim 16, wherein said forming step further comprises the step of:
polishing said tip portion to form at least two side portions on said tip portion, each said side portion further comprising a surface extending from an outer peripheral of said optical fibre toward said endmost face of said tip portion.
18. The method of claim 17, wherein said surface of each said side portion has an edge extending toward said endmost face of said tip portion, whereby said edges of said side portions contacting said endmost face.
19. The method of claim 18, wherein said surfaces of said side portions are symmetrical about said endmost face of said tip portion and said tip portion is in a substantially wedge shape.
20. The method of claim 19, wherein said forming step further comprises the step of:
polishing said tip portion to form a first chamfer portion positioned at a first end of said wedge.
21. The method of claim 20, wherein said forming step further comprises the step of:
polishing said tip portion to form a second chamfer portion positioned at a second end of said wedge opposite to said first end.
22. The method of claim 16, wherein said method further comprises the step of:
flaming said tip portion of said fibre after said forming step to provide a lens on said tip portion.
23. The method of claim 22, wherein said lens is formed on an area encompassing at least a part of said endmost face.
24. The method of claim 16, wherein said expanding step is a thermal expanding process.
25. The method of claim 16, wherein said diameter of said optical fibre is 125 \u03bcm.
26. The method of claim 16, wherein said optical fibre is a single mode optical fibre.
27. The method of claim 16, wherein an angle between a normal of said endmost face and said optical axis is approximately 6 degrees.
28. (canceled)