1. A multimode optical fiber, comprising:
a central core surrounded by an outer optical cladding, said central core having (i) an outer radius a, (ii) a transition radius rt that is less than the outer radius a, (iii) a maximum refractive index n0, (iv) a minimum refractive index nc1, and (v) a graded-index profile n(r) that is a function of the radial distance r from the center of said central core;
wherein said central core’s graded-index profile n(r) is defined by the following equation:
n
\ue8a0
(
r
)
=
n
0
\ue89e
1
–
2
\ue89e
\u0394
\ue8a0
(
r
a
)
\u03b1
\ue8a0
(
r
)
where:
\u0394
=
(
n
0
2
–
n
cl
2
)
2
\ue89e
n
0
2
wherein \u0394 is about 1.9 percent or greater;
wherein the alpha parameter \u03b1(r) is a function of the radial distance r from the center of said central core, said alpha parameter \u03b1(r) having two or more different values along radial positions from said central core’s center to said central core’s outer radius a;
wherein, for a radial position less than said central core’s transition radius rt, the alpha parameter \u03b1(r) has a first alpha-value \u03b11;
wherein, for a radial position greater than said central core’s transition radius rt, the alpha parameter \u03b1(r) has a second alpha-value \u03b12;
wherein the first alpha-value \u03b11 is greater than the second alpha-value \u03b12; and
wherein said central core’s graded-index profile n(r) and the graded-index profile’s first derivative dn(r)dr are substantially continuous along radial positions from said central core’s center to said central core’s outer radius a.
2. The multimode optical fiber according to claim 1, wherein, at a wavelength of 850 nanometers, the multimode optical fiber has an effective modal bandwidth (EMB) of about 1000 MHz\xb7km or greater.
3. The multimode optical fiber according to claim 1, wherein, at a wavelength of 850 nanometers, the multimode optical fiber has an effective modal bandwidth (EMB) of about 3000 MHz\xb7km or greater.
4. The multimode optical fiber according to claim 1, wherein, at a wavelength of 850 nanometers, the multimode optical fiber has an overfilled launch bandwidth (OFL-BW) of about 1000 MHz\xb7km or greater.
5. The multimode optical fiber according to claim 1, wherein, at a wavelength of 850 nanometers, the multimode optical fiber has an overfilled launch bandwidth (OFL-BW) of about 3000 MHz\xb7km or greater.
6. The multimode optical fiber according to claim 1, wherein said central core’s graded-index profile n(r) is defined by the following power equation:
n
\ue8a0
(
r
)
=
{
n
1
\xb7
1
–
2
\xb7
\u0394
1
\xb7
(
r
a
)
\u03b1
1
0
\u2264
r
\u2264
r
t
n
2
\xb7
1
–
2
\xb7
\u0394
2
\xb7
(
r
a
)
\u03b1
2
r
t
\u2264
r
\u2264
a
n
cl
\ue8a0
(
r
)
a
<
r
where:
\u0394
1
=
\u03b1
2
\ue89e
\u0394
\ue8a0
(
r
t
a
)
\u03b1
2
–
\u03b1
1
\u03b1
1
+
(
\u03b1
2
–
\u03b1
1
)
\ue89e
(
r
t
a
)
\u03b1
2
\ue89e
,
\ue89e
\u0394
2
=
\u03b1
1
\ue89e
\u0394
(
1
–
2
\ue89e
\u0394
)
\xb7
(
\u03b1
2
–
\u03b1
1
)
\xb7
(
r
t
a
)
\u03b1
2
+
\u03b1
1
\ue89e
,
\ue89e
n
1
=
n
cl
1
–
2
\ue89e
\u0394
,
and
n
2
=
n
cl
\xb7
(
1
–
2
\ue89e
\u0394
)
\xb7
(
\u03b1
1
–
\u03b1
2
)
\xb7
(
r
t
a
)
\u03b1
2
–
\u03b1
1
(
1
–
2
\ue89e
\u0394
)
\xb7
(
(
\u03b1
1
–
\u03b1
2
)
\xb7
(
r
t
a
)
\u03b1
2
–
\u03b1
1
)
.
7. The multimode optical fiber according to claim 1, wherein the first alpha-value \u03b11 is between about 2.05 and 2.10.
8. The multimode optical fiber according to claim 1, wherein the second alpha-value \u03b12 is at least 0.04 less than the first alpha-value \u03b11 such that \u03b11>\u03b12+0.04.
9. The multimode optical fiber according to claim 1, wherein the ratio rta of the transition radius rt to the central core’s outer radius a is between about 0.5 and 0.7.
10. The multimode optical fiber according to claim 1, wherein:
said central core has a diameter of about 50 microns; and
at a wavelength of 850 nanometers, the multimode optical fiber has a DMD value on the outer mask 0-23 microns of about 0.40 psm or less.
11. The multimode optical fiber according to claim 1, wherein:
said central core has a diameter of about 50 microns; and
at a wavelength of 850 nanometers, the multimode optical fiber has a DMD value on the outer mask 0-23 microns of about 0.14 psm or less.
12. The multimode optical fiber according to claim 1, wherein:
said central core has a diameter of about 80 microns; and
at a wavelength of 850 nanometers, the multimode optical fiber has a DMD value on the outer mask 0-37 microns of about 0.40 psm or less.
13. The multimode optical fiber according to claim 1, wherein:
said central core has a diameter of about 80 microns; and
at a wavelength of 850 nanometers, the multimode optical fiber has a DMD value on the outer mask 0-37 microns of about 0.20 psm or less.
14. The multimode optical fiber according to claim 1, wherein:
said central core has a diameter of about 62.5 microns; and
at a wavelength of 850 nanometers, the multimode optical fiber has a DMD value on the outer mask 0-29 microns of about 0.40 psm or less.
15. The multimode optical fiber according to claim 1, wherein:
said central core has a diameter of about 62.5 microns; and
at a wavelength of 850 nanometers, the multimode optical fiber has a DMD value on the outer mask 0-29 microns of about 0.14 psm or less.
16. The multimode optical fiber according to claim 1, comprising a depressed trench positioned between said central core and said outer optical cladding.
17. The multimode optical fiber according to claim 1, comprising:
a step cladding positioned between said central core and said outer optical cladding; and
a depressed trench positioned between said step cladding and said outer optical cladding.
18. An optical system comprising the multimode optical fiber according to claim 1.
19. The optical system according to claim 18, wherein the optical system is a Local Area Network.
20. A multimode optical fiber, comprising:
a central core surrounded by an outer optical cladding, said central core having (i) an outer radius a, (ii) a transition radius rt that is less than the outer radius a, (iii) a maximum refractive index n0, (iv) a minimum refractive index nc1, and (v) a graded-index profile n(r) that is a function of the radial distance r from the center of said central core;
wherein said central core’s graded-index profile n(r) has a first alpha-value \u03b11 and a second alpha-value \u03b12;
wherein the first alpha-value \u03b11 defines said central core’s graded-index profile n(r) from said central core’s center to said central core’s transition radius rt;
wherein the second alpha-value \u03b12 defines said central core’s graded-index profile n(r) from said central core’s transition radius rt to said central core’s outer radius a;
wherein the first alpha-value \u03b11 is greater than the second alpha-value \u03b12; and
wherein said central core’s graded-index profile n(r) and the graded-index profile’s first derivative dn(r)dr are substantially continuous along radial positions from said central core’s center to said central core’s outer radius a.
21. The multimode optical fiber according to claim 20, comprising a depressed trench positioned between said central core and said outer optical cladding.
22. The multimode optical fiber according to claim 20, wherein, at a wavelength of 850 nanometers, the multimode optical fiber has an effective modal bandwidth (EMB) of about 2000 MHz\xb7km or greater.
23. The multimode optical fiber according to claim 20, wherein, at a wavelength of 850 nanometers, the multimode optical fiber has an overfilled launch bandwidth (OFL-BW) of about 1500 MHz\xb7km or greater.
24. A multimode optical fiber, comprising:
a central core surrounded by an outer optical cladding, said central core having (i) an outer radius a, (ii) a transition radius rt that is less than the outer radius a, (iii) a maximum refractive index n0, (iv) a minimum refractive index nc1, and (v) a graded-index profile n(r) that is a function of the radial distance r from the center of said central core;
wherein said central core’s graded-index profile n(r) is defined by the following power equation:
n
\ue8a0
(
r
)
=
{
n
1
\xb7
1
–
2
\xb7
\u0394
1
\xb7
(
r
a
)
\u03b1
1
0
\u2264
r
\u2264
r
t
n
2
\xb7
1
–
2
\xb7
\u0394
2
\xb7
(
r
a
)
\u03b1
2
\ue89e
r
t
\u2264
r
\u2264
\u03b1
n
cl
\ue8a0
(
r
)
a
<
r
,
where:
\u0394
1
=
\u03b1
2
\ue89e
\u0394
\ue8a0
(
r
t
a
)
\u03b1
2
–
\u03b1
1
\u03b1
1
+
(
\u03b1
2
–
\u03b1
1
)
\ue89e
(
r
t
a
)
\u03b1
2
\ue89e
,
\ue89e
\u0394
2
=
\u03b1
1
\ue89e
\u0394
(
1
–
2
\ue89e
\u0394
)
\xb7
(
\u03b1
2
–
\u03b1
1
)
\xb7
(
r
t
a
)
\u03b1
2
+
\u03b1
1
,
\ue89e
n
1
=
n
cl
1
–
2
\ue89e
\u0394
,
\ue89e
n
2
=
n
cl
\ue89c
\xb7
(
1
–
2
\ue89e
\u0394
)
\xb7
(
\u03b1
1
–
\u03b1
2
)
\xb7
(
r
t
a
)
\u03b1
2
–
\u03b1
1
(
1
–
2
\ue89e
\u0394
)
\xb7
(
(
\u03b1
1
–
\u03b1
2
)
\xb7
(
r
t
a
)
\u03b1
2
–
\u03b1
1
)
;
wherein first exponent value \u03b11 defines the graded-index profile for an inner zone within said central core;
wherein second exponent value \u03b12 defines the graded-index profile for an outer zone within said central core;
wherein \u03b11>\u03b12+0.04;
wherein:
1.9
\u2264
(
n
0
2
–
n
cl
2
)
2
\ue89e
n
0
2
;
and
wherein said central core’s graded-index profile n(r) and the graded-index profile’s first derivative dn(r)dr are substantially continuous along radial positions from said central core’s center to said central core’s outer radius a.
25. The multimode optical fiber according to claim 24, comprising:
a step cladding positioned between said central core and said outer optical cladding; and
a depressed trench positioned between said step cladding and said outer optical cladding.
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. A voltage controlled oscillator comprising:
an inductor circuit including an inductor;
a plurality of variable capacitance circuits each including a variable capacitance element;
at least one capacitance switch circuit;
a negative resistance circuit; and
a frequency sensitivity controller that applies a control voltage and a control signal to the plurality of variable capacitance circuits and the at least one capacitance switch circuit,
wherein:
the inductor circuit, the plurality of variable capacitance circuits, the at least one capacitance switch circuit, and the negative resistance circuit are connected in parallel; and
the frequency sensitivity controller:
is connected to a virtual ground point for differential signals, of each of the plurality of variable capacitance circuits;
fixedly applies the control voltage for feedback control of an oscillation frequency, to at least one of the plurality of variable capacitance circuits; and
applies either one of the control voltage and the control signal, to at least one other of the plurality of variable capacitance circuits, based on at least one control signal applied to the at least one capacitance switch circuit.
2. The voltage controlled oscillator according to claim 1, wherein the frequency sensitivity controller applies the control signal to the at least one other of the plurality of variable capacitance circuits, when the control signal at a low level which does not cause switch-on is applied to all of the at least one capacitance switch circuit.
3. The voltage controlled oscillator according to claim 1, wherein the frequency sensitivity controller applies the control voltage to all of the plurality of variable capacitance circuits, when the control signal at a high level which causes switch-on is applied to all of the at least one capacitance switch circuit.
4. The voltage controlled oscillator according to claim 2, wherein the control signal applied to the at least one other of the plurality of variable capacitance circuits has two voltage levels of a low level and a high level.
5. The voltage controlled oscillator according to claim 1, wherein at least one of the variable capacitance elements of the plurality of variable capacitance circuits has an Inversion type MOS structure or an Accumulation type MOS structure.
6. A PLL circuit comprising the voltage controlled oscillator according to claim 1.
7. A radio communication device comprising the voltage controlled oscillator according to claim 1.