JP3975202B2 - Optical fiber and light source device - Google Patents

Description

  The present invention relates to an optical fiber and a light source device for emitting nonlinear phenomenon light such as supercontinuum light or idler light generated based on a nonlinear optical effect caused by incidence of an optical pulse with high peak power.

  With the development of optical communication technology, a light source that is short pulse light and has a wide wavelength width is expected. As a technique relating to such a light source, attention has been paid to the generation of supercontinuum (SC) light, which is pulsed light having a wide wavelength width, when a light pulse with high peak power is incident on an optical nonlinear medium.

  In recent years, experiments on the generation of SC light using an optical fiber (hereinafter also referred to as SC fiber) as a nonlinear medium have been made and published (Non-Patent Document 1: hereinafter referred to as Conventional Example 1). Document 2 (hereinafter referred to as Conventional Example 2), Non-Patent Document 3 (hereinafter referred to as Conventional Example 3) ", Non-Patent Document 4 (hereinafter referred to as Conventional Example 4)", Non-Patent Document 5 (hereinafter referred to as Conventional Example) Called Example 5) etc.)).

  Conventional Example 1 generates SC light when a picosecond pulse light having a central wavelength in the zero dispersion region is incident on an optical fiber having a different wavelength dispersion (normal dispersion or anomalous dispersion) or a different length. The results of the experiment are disclosed. It is disclosed that the band of SC light is wider when the optical fiber has anomalous dispersion than when it has normal dispersion.

  Conventional example 2 discloses experimental results of generation of SC light when pulsed light from a semiconductor laser (LD) is incident on optical fibers having different wavelength dispersion (dispersion flat or dispersion shift) or length. It is disclosed that the band of SC light is wider when the optical fiber has dispersion flat type dispersion than when it has dispersion shift type dispersion.

  Conventional example 3 is an SC optical fiber in which SC light is used when a dispersion shifted fiber having a length of 3 [km], a wavelength of 1541 nm and a dispersion value of 0.1 [ps / nm / km] is used. The outbreak is disclosed.

Conventional examples 4 and 5 disclose spectra at the incident end and the output end when a dispersion-shifted fiber is used as the optical fiber for SC light.
"Mori et al .: 1992 IEICE Autumn Conference C-255, pp4-277" "Mori et al .: 1993 IEICE Autumn Meeting B-920, pp4-161" "T. Morioka et al .: ELECTRONICS LETTERS, 7th July 1994, Vol. 30, No. 14, pp 1166-1168" "T. Morioka et al .: OFC '96, PD21, 1996" “T. Morioka et al .: ELECTRONICS LETTERS, 22nd June 1995, Vol. 31, No. 13”

Conventional examples 1 to 5 disclose the SC light . The present invention has been made in view of the above, and provides an optical fiber and a light source device suitable for efficiently generating nonlinear phenomenon light, which is idler light, regardless of the wavelength of excitation light. For the purpose.

An optical fiber according to claim 1 is an optical fiber that receives pump light having a wavelength different from that of signal light and generates non-linear phenomenon light that is idler light in a predetermined wavelength region, and has a dispersion slope in the signal light wavelength band. The absolute value of is 0.04 (ps / nm ² / km) or less, and the zero dispersion wavelength is increased or decreased by 5 nm or more in the longitudinal direction of the optical fiber.

  The optical fiber according to claim 2 is characterized in that chromatic dispersion decreases from a positive value to a negative value as the pulsed light travels in a dispersion decreasing region provided in a main generation region of nonlinear phenomenon light.

  The optical fiber according to claim 3 is characterized in that the dispersion decreasing region has a zero dispersion wavelength of 1.5 μm band at a predetermined position.

  An optical fiber according to a fourth aspect is characterized in that the dispersion reduction region includes a polarization maintaining fiber.

  The optical fiber according to claim 5 is characterized in that the relative refractive index difference of the core with respect to quartz is + 1.2% or more, and the relative refractive index difference with respect to quartz in the vicinity of the core of the cladding is −0.6% or less. .

In the optical fiber according to claim 6, the dispersion slope in the predetermined wavelength region of the dispersion decreasing region is not less than −0.1 (ps / nm ² / km) and not more than 0.1 (ps / nm ² / km). It is characterized by.

In the optical fiber according to the seventh aspect, the peak power P _peak of the pulse light, the nonlinear refractive index n ₂ of the dispersion reduction region, and the effective core area A _eff are (n ₂ / A _eff ) · P _peak > 4.5 × It is characterized by satisfying a relationship of 10 ⁻¹⁰ .

The optical fiber according to claim 8 is characterized in that the nonlinear refractive index n ₂ is 4 × 10 ⁻²⁰ (m ² / W) or more.

The light source device according to claim 9, characterized in that it comprises a said optical fiber, and a light source for generating excitation light (pumping light).

As described above, the nonlinear phenomenon light is idler light .

The light source device according to claim 10 is characterized in that the wavelength of the pump light is variable.

As described above in detail, according to the optical fiber of the present invention, it is a generation region of nonlinear phenomenon light that is idler light, and at least partly without increasing chromatic dispersion in the direction in which the light should travel. Therefore, when high peak pulse light is input to the dispersion reduction region of the optical fiber of the present invention, self-phase modulation is effective at least from the beginning of the incident, and four-wave mixing is more efficient from the middle. Therefore, non-linear phenomenon light is efficiently generated.

  Embodiments of an optical fiber and a light source device according to the present invention will be described below with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  (First embodiment)

  FIG. 1 is a configuration diagram of a first embodiment of a light source device of the present invention. As shown in FIG. 1, this apparatus receives (a) an optical pulse generator 100 that generates pulsed light of a predetermined wavelength, and (b) receives and amplifies the pulsed light output from the optical pulse generator 100. An optical amplifier 200 that outputs high-peak pulse light; and (c) an optical fiber 310 that inputs and propagates the high-peak pulse light output from the optical amplifier 200 to generate and output SC light.

FIG. 2 is a configuration diagram of the optical fiber 310 and shows the distribution of chromatic dispersion in the longitudinal direction (light traveling direction). As shown in FIG. 2, in the optical fiber 310, the chromatic dispersion D _IN at the incident end of the high peak pulse light from the optical amplifier 200 has a positive value, and the chromatic dispersion D linearly decreases along the longitudinal direction. To do.

  In the light source device of the present embodiment, first, the optical pulse generator 100 generates short pulse light having a predetermined wavelength. The short pulse light output from the optical pulse light generator 100 is input to the optical amplifier 200, amplified, and output as high peak pulse light. Then, the high peak pulse light output from the optical amplifier 200 is input to the optical fiber 310.

  When high peak pulse light is input to the optical fiber 310, the refractive index felt by the light changes due to the optical Kerr effect, and self-phase modulation of the light wave occurs. As a result, a wavelength distribution is generated in the optical pulse in the optical fiber 310. Since the light input to the optical fiber 310 travels through the anomalous dispersion region where the chromatic dispersion has a positive value, pulse compression proceeds in the anomalous dispersion region where the longer the wavelength, the slower the group velocity. As the dispersion decreases in the longitudinal direction, the peak power increases because the pulses are more compulsorily compressed. This further promotes the nonlinear effect and leads to the expansion of the spectrum.

  The compressed light pulse includes light of a certain wavelength range, but is strongly influenced by four-wave mixing due to the optical Kerr effect while the dispersion value changes from positive to negative. Light of a wide wavelength range is generated. In this way, SC light is generated.

As shown in FIG. 2, the optical fiber 310 has a chromatic dispersion D that is a function of the position Z in the traveling direction,
D (Z) = D _IN − (ΔD) · Z (3)
It is expressed. Therefore, when light travels, spectrum expansion due to self-phase modulation is less likely to occur, but the occurrence of phase differences between light of different wavelengths due to travel gradually decreases. For this reason, the chromatic dispersion D does not depend on the position Z in the traveling direction,
D (Z) = D _IN (4)
Compared with the case where the above holds, the temporal overlap of light of different wavelengths increases, and four-wave mixing is efficiently generated.

  In other words, the optical fiber 310 has a dispersion reduction region that starts with anomalous dispersion and decreases chromatic dispersion in the direction in which the light should travel. In the dispersion reduction region that is the main part of SC light generation, pulse compression by anomalous dispersion SC light is generated by nonlinear phenomena such as self-phase modulation and four-wave mixing.

  Then, since the chromatic dispersion changes in the traveling direction of the light, a kind of scanning of the zero dispersion wavelength is performed in the vicinity of the wavelength of the light where the four-wave mixing occurs. Light wave mixing is likely to occur, and light having a wide wavelength range is generated.

  In the present embodiment, it is desirable that the absolute value of the dispersion slope of the optical fiber is small. This is because, when the absolute value of the dispersion slope is small, the temporal overlap between the light beams having different wavelengths increases, so that four-wave mixing is likely to occur.

  In addition, as the absolute value of the integral value in the longitudinal direction of the dispersion slope is smaller, the temporal overlap with light having different wavelengths increases, so that four-wave mixing is likely to occur.

  Further, it is preferable that the chromatic dispersion value in the dispersion decreasing region changes from a positive value to a negative value.

  In a fiber with a dispersion slope that is positive in a predetermined wavelength range, when the chromatic dispersion value has a positive value, light having a wavelength shorter than the wavelength of the incident high peak pulse light is likely to be generated, and the chromatic dispersion value is negative. In the case of having a value of λ, light having a wavelength longer than the wavelength of the incident high peak pulse light is likely to be generated.

  Therefore, if the chromatic dispersion value in the dispersion decreasing region changes from a positive value to a negative value, light in both short and long wavelength bands is efficiently generated with respect to the wavelength of the incident high peak pulse light. Therefore, SC light in a wide wavelength range is generated.

Furthermore, the Kerr effect, which is a nonlinear optical effect that causes self-phase modulation and four-wave mixing, is more likely to occur as the nonlinear refractive index increases and the light intensity density increases. In order to obtain a wavelength width of several tens of nanometers or more, between the nonlinear refractive index n ₂ , the effective core area A _eff, and the peak power P _peak of the high peak pulse light,
(N ₂ / A _eff ) · P _peak > 0.03 × 10 ⁻⁸ [1 / W] × 1.5 [W] = 0.045 × 10 ⁻⁸ (1)
It is necessary that this relationship holds.

FIG. 3 shows the relationship between the ratio value of the nonlinear refractive index n ₂ and the effective core area A _eff and the wavelength width of the SC light when the peak power P _peak of the high peak pulse light is 1.5 [W]. It is a graph to show. In the following, the length of the optical fiber is denoted by L, and the dispersion slope is denoted by D _SLOP .

In this measurement, as the optical fiber 310,
D _IN = 1 to 4 [ps / nm / km]
ΔD = 0.5 to 2 [ps / nm / km ² ]
D _SLOP = 0.035 [ps / nm ² / km]
L = 3 [km]
The optical fiber of the characteristic was used.

The high peak pulse light input to the optical fiber 310 is
Pulse center wavelength (λ0) = 1550 [nm]
Pulse peak power = 1.5 [W]
Pulse width = 3.5 [ps] (full width at half maximum)
It was.

Then, the value of the ratio between the nonlinear refractive index n2 and the effective core area A _eff and the wavelength width of the SC light were calculated by combining various D _IN and ΔD.

From FIG. 3, when the peak power P _peak of the high peak pulse light is 1.5 [W], if n2 / A _eff > 0.03 × 10 ⁻⁸ [1 / W], the relationship between D _IN and ΔD Regardless of the combination, SC light having an optical frequency displacement width wf of about 5000 [GHz] or more was generated and output.

The relationship between the optical frequency displacement width wf and the wavelength range wλ is
wλ- (λ0 ² / C) · wf (5)
Where C: speed of light,
When the width wf of the optical frequency displacement is expressed in [THz] and the wavelength range wλ is expressed in [nm], λ0 = 1550 [nm]
wλ ~ 8wf (6)
It becomes.

That is, when the peak power P _peak of the high peak pulse light is 1.5 [W],
n ₂ / A _eff > 0.03 × 10 ⁻⁸ [1 / W]
If so, SC light having a wavelength width of about 40 nm or more is output.

  In the present embodiment, it is preferable that the optical fiber 310 is a polarization maintaining fiber and has polarization maintaining characteristics. This is because four-wave mixing occurs best when two interacting lights have the same polarization plane direction.

  Below, the Example of the light source device of this embodiment is described.

  Example 1

  FIG. 4 is a configuration diagram of the light source device according to the first embodiment. As shown in FIG. 4, this apparatus inputs (a) an optical pulse generator 100 that generates pulsed light of a predetermined wavelength, and (b) receives and amplifies the pulsed light output from the optical pulse generator 100. An optical amplifier 200 that outputs high peak pulse light; and (c) an optical fiber 311 that inputs and propagates the high peak pulse light output from the optical amplifier 200 to generate and output SC light.

The optical fiber 311 is
D _IN = 1 [ps / nm / km]
ΔD = 1/3 [ps / nm / km ² ]
D _SLOP = 0.07 [ps / nm ² / km]
L = 3 [km]
n ₂ = 2.0 × 10 ⁻²⁰ [m ² / W]
A _eff = 50 [μm ² ]
This is a dispersion-shifted fiber.

  FIG. 5 is a graph showing the spectra of high peak pulse light and generated SC light in this example. FIG. 5A is a graph showing the spectrum of the high peak pulse light input to the optical fiber 311, and FIG. 5B is a graph showing the spectrum of the SC light output from the optical fiber 311.

The high peak pulse light input to the optical fiber 311 has a spectral distribution shown in FIG.
Pulse center wavelength (λ0) = 1550 [nm]
Pulse peak power = 1.5 [W]
Pulse width = 3.5 [ps] (full width at half maximum)
It was.

  As shown in FIG. 5B, in the light source device of this embodiment, the width wf of the optical frequency displacement of the flat peak portion in the output spectrum is about 5000 [GHz] in the vicinity of the wavelength = 1550 [μm]. SC light was generated and output. That is, in the light source device of this example, SC light having a wavelength width of about 40 nm was output.

  (Example 2)

  FIG. 6 is a configuration diagram of the light source device according to the second embodiment. As shown in FIG. 6, this apparatus receives (a) an optical pulse generator 100 that generates pulsed light of a predetermined wavelength, and (b) receives and amplifies the pulsed light output from the optical pulse generator 100. , An optical amplifier 200 that outputs high peak pulse light; and (c) an optical fiber 312 that inputs and propagates the high peak pulse light output from the optical amplifier 200 to generate and output SC light.

The optical fiber 312 is
D _IN = 1 [ps / nm / km]
ΔD = 0.5 [ps / nm / km ² ]
D _SLOP = 0.01 [ps / nm ² / km]
L = 3 [km]
n ₂ = 2.0 × 10 ⁻²⁰ [m ² / W]
A _eff = 50 [μm ² ]
The dispersion flat fiber.

  FIG. 7 is a graph showing the spectrum of the SC light generated in this example. The high peak pulse light input to the optical fiber 312 was the same as in Example 1.

  As shown in FIG. 7, in the light source device of the present embodiment, SC light having an optical frequency displacement width wf of about 12000 [GHz] near the wavelength = 1550 [μm] in the flat peak portion of the output spectrum. Generated and output. That is, the light source device of this example output SC light having a wavelength width of about 96 nm.

  In this example, the wavelength width of the SC light was expanded as compared with Example 1.

  (Example 3)

  FIG. 8 is a configuration diagram of the light source device according to the third embodiment. As shown in FIG. 8, this apparatus receives (a) an optical pulse generator 100 that generates pulsed light of a predetermined wavelength, and (b) receives and amplifies the pulsed light output from the optical pulse generator 100. An optical amplifier 200 that outputs high-peak pulse light; and (c) an optical fiber 313 that inputs and propagates the high-peak pulse light output from the optical amplifier 200 to generate and output SC light.

The optical fiber 313 is
D _IN = 0.7 [ps / nm / km]
ΔD = 1/3 [ps / nm / km ² ]
D _SLOP = 0.01 [ps / nm ² / km]
L = 3 [km]
n ₂ = 2.0 × 10 ⁻²⁰ [m ² / W]
A _eff = 50 [μm ² ]
The dispersion flat fiber.

  FIG. 9 is a graph showing the spectrum of the SC light generated in this example. The high peak pulse light input to the optical fiber 313 was the same as that in Example 1.

  As shown in FIG. 9, in the light source device of this example, the width wf of the optical frequency displacement of the flat peak portion (within about ± 5 [dB]) in the output spectrum is around the wavelength = 1550 [μm]. About 10,000 [GHz] SC light was generated and output. That is, in the light source device of this example, SC light having a wavelength width of about 80 nm was output.

  In this example, the wavelength width of the SC light was expanded as in Example 2, compared with Example 1.

  Example 4

  In this embodiment, the relationship between the wavelength width of SC light and the dispersion slope DSLOP is systematically measured.

  FIG. 10 is a configuration diagram of the light source device according to the fourth embodiment. As shown in FIG. 10, this apparatus inputs (a) an optical pulse generator 100 that generates pulsed light of a predetermined wavelength, and (b) receives and amplifies the pulsed light output from the optical pulse generator 100. An optical amplifier 200 that outputs high peak pulse light; and (c) an optical fiber 314 that inputs and propagates the high peak pulse light output from the optical amplifier 200 to generate and output SC light.

The optical fiber 314 is
D _IN = 2 [ps / nm / km]
ΔD = 1 [ps / nm / km ² ]
D _SLOP = 0.01 to 0.2 [ps / nm ² / km]
L = 3 [km]
n ₂ = 6.0 × 10 ⁻²⁰ [m ² / W]
A _eff = 10 [μm ² ]
The dispersion flat fiber.

11 and 12 are graphs showing the spectrum of the SC light generated in this example. 11A shows a case where D _SLOP = 0.2, FIG. 11B shows a case where D _SLOP = 0.1, and FIG. 11C shows a case where D _SLOP = 0.08. for _D SLOP = 0.05, as shown in FIG. 12 (a) when the _D SLOP = 0.03, FIG. 12 (b) for _D SLOP = 0.02, and, FIG. 12 (c) _{D SLOP} = Indicates the case of 0.01. The high peak pulse light input to the optical fiber 314 was the same as in Example 1.

  As shown in FIGS. 11 and 12, when the DSLOP is 0.1 or less and the wavelength = 1550 [μm], the width wf of the optical frequency displacement of the flat peak portion in the output spectrum is about 10,000 [GHz]. SC light was generated and output. That is, in the light source device of this example, SC light having a DSLOP of 0.1 or less and a wavelength width of about 80 nm was output.

  (Example 5)

  FIG. 13 is a configuration diagram of the light source device of the fifth embodiment. As shown in FIG. 13, this apparatus inputs (a) an optical pulse generator 100 that generates pulsed light of a predetermined wavelength, and (b) receives and amplifies the pulsed light output from the optical pulse generator 100. An optical amplifier 200 that outputs high peak pulse light; and (c) an optical fiber 315 that inputs and propagates the high peak pulse light output from the optical amplifier 200 to generate and output SC light.

The optical fiber 315 is
D _IN = 2 [ps / nm / km]
ΔD = 1 [ps / nm / km ² ]
D _SLOP : Linearly decreasing from 0.01 to _−0.01 [ps / nm ² / km] L = 3 [km]
n ₂ = 3.0 × 10 ⁻²⁰ [m ² / W]
A _eff = 50 [μm ² ]
The dispersion flat fiber.

  FIG. 14 is a graph showing the spectrum of the SC light generated in this example. The high peak pulse light input to the optical fiber 315 was the same as in Example 1.

  As shown in FIG. 14, in the light source device of the present embodiment, SC light having an optical frequency displacement width wf of about 30000 [GHz] near the wavelength = 1550 [μm] in the flat peak portion of the output spectrum. Generated and output. That is, in the light source device of this example, SC light having a wavelength width of about 240 nm was output.

  (Second Embodiment)

  FIG. 15 is a configuration diagram of a second embodiment of the light source device of the present invention. As shown in FIG. 15, this apparatus inputs (a) an optical pulse generator 100 that generates pulsed light of a predetermined wavelength, and (b) receives and amplifies the pulsed light output from the optical pulse generator 100. An optical amplifier 200 that outputs high peak pulse light; and (c) an optical fiber 320 that inputs and propagates the high peak pulse light output from the optical amplifier 200 to generate and output SC light.

  FIG. 16 is a graph showing the distribution of chromatic dispersion in the longitudinal direction (light traveling direction) of the optical fiber 320.

  Compared with the first embodiment, in the present embodiment, the optical fiber 320 has a positive value of the chromatic dispersion DIN at the incident end of the high peak pulse light from the optical amplifier 200, as shown in FIG. The same is true except that the chromatic dispersion D decreases nonlinearly along the longitudinal direction.

  In the light source device of the present embodiment, as in the first embodiment, the short pulse light generated by the optical pulse generator 100 is input to the optical amplifier 200, amplified, and output as high peak pulse light. The high peak pulse light output from 200 is input to the optical fiber 320.

  Thereafter, as in the first embodiment, when high peak pulse light is input to the optical fiber 320, the refractive index felt by the light changes due to the optical Kerr effect, and self-phase modulation of the light wave occurs. As a result, a wavelength distribution is generated in the optical pulse in the optical fiber 320. Since the light input to the optical fiber 320 travels through the anomalous dispersion region where the chromatic dispersion has a positive value, pulse compression proceeds in the anomalous dispersion region where the longer the wavelength, the slower the group velocity. If the dispersion decreases in the longitudinal direction, the pulse is more compulsorily compressed, so that the peak power increases. This further promotes the nonlinear effect and leads to the expansion of the spectrum.

  The compressed light pulse includes light of a certain wavelength range, but is strongly influenced by four-wave mixing due to the optical Kerr effect while the dispersion value changes from positive to negative. Light of a wide wavelength range is generated. In this way, SC light is generated.

  In the present embodiment, similarly to the first embodiment, it is desirable that the absolute value of the dispersion slope of the optical fiber is small, and the wavelength is different as the absolute value of the integral value in the longitudinal direction of the dispersion slope is small. Since the temporal overlap with light increases, four-wave mixing tends to occur.

Further, as in the first embodiment, the Kerr effect, which is a nonlinear optical effect that causes self-phase modulation and four-wave mixing, is more likely to occur as the nonlinear refractive index increases and the light intensity density increases. . In order to obtain a wavelength width of several tens of nanometers or more, between the nonlinear refractive index n ₂ , the effective core area A _eff, and the peak power P _peak of the high peak pulse light,
(N ₂ / A _eff ) · P _peak > 0.03 × 10 ⁻⁸ [1 / W] × 1.5 [W] = 0.045 × 10 ⁻⁸ (1)
It is necessary that this relationship holds.

  In the present embodiment, similarly to the first embodiment, it is preferable that the optical fiber 320 is a polarization maintaining fiber and has polarization plane maintaining characteristics. This is because four-wave mixing occurs best when two interacting lights have the same polarization plane direction.

  Hereinafter, examples of the present embodiment will be described.

  (Example 6)

  FIG. 17 is a configuration diagram of the light source device according to the sixth embodiment. As shown in FIG. 17, this apparatus inputs (a) an optical pulse generator 100 that generates pulsed light of a predetermined wavelength, and (b) receives and amplifies pulsed light output from the optical pulse generator 100. An optical amplifier 200 that outputs high peak pulse light; and (c) an optical fiber 321 that inputs and propagates the high peak pulse light output from the optical amplifier 200 to generate and output SC light.

The optical fiber 321 is
D _IN = 1.8 [ps / nm / km]
D _OUT = −0.1 [ps / nm / km]
D _SLOP = 0.01 [ps / nm ² / km]
L = 3 [km]
n ₂ = 2.0 × 10 −20 [m ² / W]
A _eff = 50 [μm ² ]
The dispersion flat fiber.

  FIG. 18 is a graph showing measurement results of SC light generation in this example. The high peak pulse light input to the optical fiber 321 was the same as in Example 1.

  As shown in FIG. 18, in the light source device of the present embodiment, SC light having an optical frequency displacement width wf of about 12000 [GHz] near the wavelength = 1550 [μm] in the flat peak portion of the output spectrum. Generated and output. That is, the light source device of this example output SC light having a wavelength width of about 96 nm.

  (Third embodiment)

  FIG. 19 is a configuration diagram of a third embodiment of the light source device of the present invention. As shown in FIG. 19, this apparatus inputs (a) an optical pulse generator 100 that generates pulsed light of a predetermined wavelength, and (b) receives and amplifies the pulsed light output from the optical pulse generator 100. , An optical amplifier 200 that outputs high peak pulse light; and (c) an optical fiber 330 that inputs and propagates the high peak pulse light output from the optical amplifier 200 to generate and output SC light.

  FIG. 20 is a graph showing a distribution of chromatic dispersion in the longitudinal direction (light traveling direction) of the optical fiber 330.

This embodiment is different from the first embodiment, it the optical fiber 320, as shown in FIG. 20, the wavelength dispersion D _IN at the entrance end of the high-peak pulse light from the optical amplifier 200 is a positive value Is the same except that the chromatic dispersion D decreases discretely along the longitudinal direction.

  Such an optical fiber is obtained by connecting an optical fiber having a length Li of each section and having a chromatic dispersion value Di of each section.

  In the light source device of the present embodiment, as in the first embodiment, the short pulse light generated by the optical pulse generator 100 is input to the optical amplifier 200, amplified, and output as high peak pulse light. The high peak pulse light output from 200 is input to the optical fiber 330.

  Thereafter, as in the first embodiment, when high peak pulse light is input to the optical fiber 330, the refractive index felt by the light changes due to the optical Kerr effect, and self-phase modulation of the light wave occurs. As a result, a wavelength distribution is generated in the optical pulse in the optical fiber 330. Since the light input to the optical fiber 330 travels through the anomalous dispersion region where the chromatic dispersion has a positive value, pulse compression proceeds in the anomalous dispersion region where the longer the wavelength, the slower the group velocity. If the dispersion decreases in the longitudinal direction, the pulse is more compulsorily compressed, so that the peak power increases. This further promotes the nonlinear effect and leads to the expansion of the spectrum.

  The compressed light pulse includes light of a certain wavelength range, but is strongly influenced by four-wave mixing due to the optical Kerr effect while the dispersion value changes from positive to negative. Light of a wide wavelength range is generated. In this way, SC light is generated.

  In the present embodiment, similarly to the first embodiment, it is desirable that the absolute value of the dispersion slope of the optical fiber is small, and the wavelength is different as the absolute value of the integral value in the longitudinal direction of the dispersion slope is small. Since the temporal overlap with light increases, four-wave mixing tends to occur.

Further, as in the first embodiment, the Kerr effect, which is a nonlinear optical effect that causes self-phase modulation and four-wave mixing, is more likely to occur as the nonlinear refractive index increases and the light intensity density increases. . In order to obtain a wavelength width of several tens of nanometers or more, between the nonlinear refractive index n ₂ , the effective core area A _eff, and the peak power P _peak of the high peak pulse light,
(N ₂ / A _eff ) · P _peak > 0.03 × 10 ⁻⁸ [1 / W] × 1.5 [W] = 0.045 × 10 ⁻⁸ (1)
It is necessary that this relationship holds.

  In the present embodiment, similarly to the first embodiment, it is preferable that the optical fiber 330 is a polarization maintaining fiber and has polarization plane maintaining characteristics. This is because four-wave mixing occurs best when two interacting lights have the same polarization plane direction.

  Hereinafter, examples of the present embodiment will be described.

  (Example 7)

  FIG. 21 is a configuration diagram of the light source device of the seventh embodiment. As shown in FIG. 21, this apparatus receives (a) an optical pulse generator 100 that generates pulsed light of a predetermined wavelength, and (b) receives and amplifies the pulsed light output from the optical pulse generator 100. An optical amplifier 200 that outputs high peak pulse light; and (c) an optical fiber 331 that inputs and propagates the high peak pulse light output from the optical amplifier 200 to generate and output SC light.

In the optical fiber 331, as shown in FIG. 21, the length Li of each section is all 500 [m],
D1 = 2.0 [ps / nm / km],
D2 = 1.4 [ps / nm / km],
D3 = 0.8 [ps / nm / km],
D4 = 0.2 [ps / nm / km],
D5 = 0.01 [ps / nm / km],
D6 = −0.2 [ps / nm / km],
D _SLOP = 0.01 [ps / nm ² / km]
L = 3 [km]
n ₂ = 2.0 × 10 ⁻²⁰ [m ² / W]
A _eff = 50 [μm ² ]
It has the following characteristics.

  FIG. 22 is a graph showing the spectrum of the SC light generated in this example. The high peak pulse light input to the optical fiber 321 was the same as in Example 1.

  As shown in FIG. 22, in the light source device of the present embodiment, SC light having an optical frequency displacement width wf of about 12000 [GHz] in the vicinity of the wavelength = 1550 [μm] in the flat peak portion of the output spectrum. Generated and output. That is, the light source device of this example output SC light having a wavelength width of about 96 nm.

  (Fourth embodiment)

  FIG. 23 is a configuration diagram of a fourth embodiment of the light source device of the present invention. As shown in FIG. 23, this apparatus has (a) an optical pulse generator 100 that generates a pulsed light of a predetermined wavelength, and (b) a pulsed light output from the optical pulse generator 100 that is input and amplified. An optical amplifier 200 that outputs high-peak pulse light; and (c) an optical fiber 341 and an optical fiber that generate and output SC light by inputting and propagating the high-peak pulse light output from the optical amplifier 200. And an optical fiber 340 made of 342.

  FIG. 24 is a graph showing the distribution of chromatic dispersion in the longitudinal direction (light traveling direction) of the optical fiber 340. As shown in FIG. 24, (i) In the optical fiber 341, the chromatic dispersion DIN at the incident end of the high peak pulse light from the optical amplifier 200 is a positive value, and the chromatic dispersion D is linear along the longitudinal direction. (Ii) In the optical fiber 342, the chromatic dispersion has a small value.

  Such an optical fiber is obtained by connecting an optical fiber having a length Li of each section and having a chromatic dispersion value Di of each section.

  In the light source device of the present embodiment, as in the first embodiment, the short pulse light generated by the optical pulse generator 100 is input to the optical amplifier 200, amplified, and output as high peak pulse light. The high peak pulse light output from 200 is input to the optical fiber 341 of the optical fiber 340.

  Thereafter, as in the first embodiment, when high peak pulse light is input to the optical fiber 341, the refractive index felt by the light changes due to the optical Kerr effect, and self-phase modulation of the light wave occurs. As a result, a wavelength distribution is generated in the optical pulse in the optical fiber 341. Since the light input to the optical fiber 341 travels through the anomalous dispersion region where the chromatic dispersion has a positive value, pulse compression proceeds in the anomalous dispersion region where the longer the wavelength, the slower the group velocity. If the dispersion decreases in the longitudinal direction, the pulse is more compulsorily compressed, so that the peak power increases. This further promotes the nonlinear effect and leads to the expansion of the spectrum.

  The compressed light pulse includes light of a wavelength in a certain wavelength range. While the dispersion value changes from positive to negative, it is strongly influenced by four-wave mixing due to the optical Kerr effect. Light of a wide wavelength range is generated. In this way, SC light is generated.

  The SC light generated in this way is output from the optical fiber 341, input to the optical fiber 342, and output after propagating through the optical fiber 342.

  In the present embodiment, similarly to the first embodiment, it is desirable that the absolute value of the dispersion slope of the optical fiber 341 is small, and the smaller the absolute value of the integral value in the longitudinal direction of the dispersion slope, the smaller the wavelength. Since the temporal overlap with different lights increases, four-wave mixing is likely to occur.

Furthermore, as in the first embodiment, the Kerr effect, which is a nonlinear optical effect that causes self-phase modulation and four-wave mixing in the optical fiber 341, increases as the nonlinear refractive index increases and the light intensity density increases. , Easy to express. In order to obtain a wavelength width of several tens of nanometers or more, between the nonlinear refractive index n ₂ , the effective core area A _eff, and the peak power P _peak of the high peak pulse light,
(N ₂ / A _eff ) · P _peak > 0.03 × 10 ⁻⁸ [1 / W] × 1.5 [W] = 0.045 × 10 ⁻⁸ (1)
It is necessary that this relationship holds.

  In the present embodiment, similarly to the first embodiment, it is preferable that the optical fiber 341 is a polarization maintaining fiber and has polarization plane maintaining characteristics. This is because four-wave mixing occurs best when two interacting lights have the same polarization plane direction.

  Hereinafter, examples of the present embodiment will be described.

  (Example 8)

  FIG. 25 is a configuration diagram of the light source device of the eighth embodiment. As shown in FIG. 25, this apparatus receives (a) an optical pulse generator 100 that generates pulsed light having a predetermined wavelength, and (b) receives and amplifies the pulsed light output from the optical pulse generator 100. An optical amplifier 200 that outputs high-peak pulse light; and (c) an optical fiber 346 and an optical fiber that generate and output SC light by inputting and propagating the high-peak pulse light output from the optical amplifier 200. And an optical fiber 345 composed of 347.

As shown in FIG.
D _IN = 0.8 [ps / nm / km],
ΔD = 2 [ps / nm / km ² ],
D _SLOP = 0.01 [ps / nm ² / km],
L = 0.5 [km]
n ₂ = 6.0 × 10 ⁻²⁰ [m ² / W]
A _eff = 10 [μm ² ]
It has the following characteristics.

Moreover, as shown in FIG.
D _IN ˜0 [ps / nm / km],
ΔD to 0 [ps / nm / km ² ],
D _SLOP = 0.01 [ps / nm ² / km],
L = 2.5 [km]
n ₂ = 6.0 × 10 ⁻²⁰ [m ² / W]
A _eff = 10 [μm ² ]
It has the following characteristics.

  FIG. 26 is a graph showing the spectrum of the SC light generated in this example. The high peak pulse light input to the optical fiber 335 was the same as that in Example 1.

  As shown in FIG. 26, in the light source device of the present embodiment, SC light having an optical frequency displacement width wf of about 10000 [GHz] near the wavelength = 1550 [μm] in the flat peak portion of the output spectrum. Generated and output. That is, in the light source device of this example, SC light having a wavelength width of about 80 nm was output.

  In this example, the same modification as the second or third embodiment with respect to the first embodiment can be made.

  (Fifth embodiment)

  FIG. 27 is a configuration diagram of a fifth embodiment of the light source device of the present invention. As shown in FIG. 27, this apparatus has (a) an optical pulse generator 100 that generates pulsed light of a predetermined wavelength, and (b) pulse light output from the optical pulse generator 100, and amplifies it. An optical amplifier 200 that outputs a high peak pulse light; and (c) an optical fiber 351 and an optical fiber that generate and output SC light by inputting and propagating the high peak pulse light output from the optical amplifier 200. 352 and an optical fiber 350 including an optical fiber 353 are provided.

  FIG. 28 is a graph showing the distribution of chromatic dispersion in the longitudinal direction (light traveling direction) of the optical fiber 350. As shown in FIG. 28, (i) the chromatic dispersion D has a small value in the optical fiber 351, and (ii) the chromatic dispersion DIN at the incident end of the high peak pulse light has a positive value in the optical fiber 352. Yes, the chromatic dispersion D decreases linearly along the longitudinal direction. (Iii) In the optical fiber 353, the chromatic dispersion D has a small value.

  Such an optical fiber is obtained by connecting an optical fiber having a length Li of each section and having a chromatic dispersion value Di of each section.

  In the light source device of the present embodiment, as in the first embodiment, the short pulse light generated by the optical pulse generator 100 is input to the optical amplifier 200, amplified, and output as high peak pulse light. The high peak pulse light output from 200 is input to the optical fiber 351 of the optical fiber 350. Then, after propagating through the optical fiber 351, the signal is input to the optical fiber 352.

  Thereafter, as in the first embodiment, when high-peak pulse light is input to the optical fiber 352, the refractive index felt by the light changes due to the optical Kerr effect, and self-phase modulation of the light wave occurs. As a result, a wavelength distribution is generated in the optical pulse in the optical fiber 352. Since the light input to the optical fiber 352 travels through the anomalous dispersion region where the chromatic dispersion has a positive value, pulse compression proceeds in the anomalous dispersion region where the longer the wavelength, the slower the group velocity. If the dispersion decreases in the longitudinal direction, the pulse is more compulsorily compressed, so that the peak power increases. This further promotes the nonlinear effect and leads to the expansion of the spectrum.

  The compressed light pulse includes light of a certain wavelength range, but is strongly influenced by four-wave mixing due to the optical Kerr effect while the dispersion value changes from positive to negative. Light of a wide wavelength range is generated. In this way, SC light is generated.

  The SC light thus generated is output from the optical fiber 352, input to the optical fiber 353, and output after propagating through the optical fiber 353.

  In the present embodiment, similarly to the first embodiment, it is desirable that the absolute value of the dispersion slope of the optical fiber 352 is small, and if the integral value in the longitudinal direction of the dispersion slope is approximately 0, the wavelength is Since the overlap in time with different light becomes almost ideal, four-wave mixing is likely to occur.

Furthermore, as in the first embodiment, the Kerr effect, which is a nonlinear optical effect that causes self-phase modulation and four-wave mixing in the optical fiber 352, increases as the nonlinear refractive index increases and the light intensity density increases. , Easy to express. In order to obtain a wavelength width of several tens of nanometers or more, between the nonlinear refractive index n ₂ , the effective core area A _eff, and the peak power P _peak of the high peak pulse light,
(N ₂ / A _eff ) · P _peak > 0.03 × 10 ⁻⁸ [1 / W] × 1.5 [W] = 0.045 × 10 ⁻⁸ (1),
It is necessary that this relationship holds.

  In this embodiment, similarly to the first embodiment, it is preferable that the optical fibers 351 and 352 are polarization maintaining fibers and have polarization plane maintaining characteristics. This is because four-wave mixing occurs best when two interacting lights have the same polarization plane direction.

  Hereinafter, examples of the present embodiment will be described.

  Example 9

  FIG. 29 is a configuration diagram of the light source device according to the ninth embodiment. As shown in FIG. 29, this apparatus receives (a) an optical pulse generator 100 that generates pulsed light of a predetermined wavelength, and (b) receives and amplifies the pulsed light output from the optical pulse generator 100. An optical amplifier 200 that outputs high-peak pulse light; and (c) an optical fiber 356 and an optical fiber that generate and output SC light by inputting and propagating the high-peak pulse light output from the optical amplifier 200. 357 and an optical fiber 355 composed of an optical fiber 358.

As shown in FIG. 29, the optical fiber 356 is
D _IN = 0.2 [ps / nm / km],
ΔD to 0 [ps / nm / km ² ],
D _SLOP = 0.035 [ps / nm ² / km],
L = 1 [km]
n ₂ = 5.0 × 10 ⁻²⁰ [m ² / W]
A _eff = 13.85 [μm ² ]
It has the following characteristics.

In addition, as shown in FIG.
D _IN = 0.8 [ps / nm / km],
ΔD = 1 [ps / nm / km ² ],
D _SLOP = 0.035 [ps / nm ² / km],
L = 1 [km]
n ₂ = 5.0 × 10 ⁻²⁰ [m ² / W]
A _eff = 13.85 [μm ² ]
It has the following characteristics.

In addition, as shown in FIG.
D _IN = 0.2 [ps / nm / km],
ΔD to 0 [ps / nm / km ² ],
D _SLOP = 0.035 [ps / nm ₂ / km],
L = 1 [km]
n ₂ = 5.0 × 10 ⁻²⁰ [m ² / W]
A _eff = 13.85 [μm ² ]
It has the following characteristics.

  FIG. 30 is a graph showing the spectrum of the SC light generated in this example. The high peak pulse light input to the optical fiber 355 was the same as in Example 1.

  As shown in FIG. 30, in the light source device of the present embodiment, SC light having an optical frequency displacement width wf of about 12000 [GHz] in the vicinity of the wavelength = 1550 [μm] in the flat peak portion of the output spectrum. Generated and output. That is, the light source device of this example output SC light having a wavelength width of about 96 nm.

  In this example, the same modification as the second or third embodiment with respect to the first embodiment can be made.

Further, as shown in FIG. 31, the zero dispersion wavelength at the predetermined position L = L0 of the optical fiber for SC light of the above embodiment matches the wavelength λ0 of the incident pulsed light. The wavelength dispersion of the incident end L = 0 of the optical fiber and _{D IN} at a wavelength .lambda.0, in the optical fiber which position has a constant dispersion slope _{D SLOP} in the wavelength range of .lambda.0 ± 20 nm.

  (Sixth embodiment)

In order to generate SC light, the dispersion slope D _SLOP does not necessarily have to be constant in the wavelength range of λ0 ± 20 nm. As shown in FIG. 32, the chromatic dispersion D is substantially constant in the wavelength range of λ0 ± 20 nm ( It may be flat (D _SLOP ≈ 0.) This optical fiber has two zero dispersion wavelengths in a wavelength range of 1530 to 1570 nm at a certain position in a predetermined length direction.

FIG. 33 shows a light source device according to the sixth embodiment using an optical fiber 360 for SC light having the characteristics shown in FIG. As shown in FIG. 33, this apparatus receives (a) an optical pulse generator 100 that generates pulsed light of a predetermined wavelength, and (b) pulse light output from the optical pulse generator 100, and amplifies it. An optical amplifier 200 that outputs high peak pulse light; and (c) an optical fiber 360 that inputs and propagates the high peak pulse light output from the optical amplifier 200 to generate and output SC light. In the optical fiber 360, the chromatic dispersion D _IN at the incident end of the high peak pulse light from the optical amplifier 200 has a positive value, and the chromatic dispersion D within the predetermined wavelength range λ0 ± 20 nm is linear along the longitudinal direction. Decrease. That is, the wavelength dispersion D of the length L = 0 is _{D IN,} chromatic dispersion D at a length L = L0 is zero, chromatic dispersion D at a length L = L is _{D OUT.}

  In the light source device of the present embodiment, first, the optical pulse generator 100 generates short pulse light having a predetermined wavelength. The short pulse light output from the optical pulse light generator 100 is input to the optical amplifier 200, amplified, and output as high peak pulse light. The high peak pulse light output from the optical amplifier 200 is input to the optical fiber 360.

  When high peak pulse light is input to the optical fiber 360, the refractive index felt by the light changes due to the optical Kerr effect, and self-phase modulation of the light wave occurs. As a result, a wavelength distribution is generated in the optical pulse in the optical fiber 360. Since the light input to the optical fiber 360 travels through the anomalous dispersion region where the chromatic dispersion D has a positive value, pulse compression proceeds in the anomalous dispersion region where the longer the wavelength, the slower the group velocity. If the dispersion decreases in the longitudinal direction, the pulse is more compulsorily compressed, so that the peak power increases. This further promotes the nonlinear effect and leads to the expansion of the spectrum.

  The compressed light pulse includes light of a certain wavelength range, but is strongly influenced by four-wave mixing due to the optical Kerr effect while the dispersion value changes from positive to negative. Light of a wide wavelength range is generated. In this way, SC light is generated.

  FIG. 34 shows the spectrum of the outgoing light emitted from this SC optical fiber 360. The length L of the optical fiber 360 is 1 km. The peak wavelength λ0 of the wavelength spectrum of this SC light is 1550 nm. If the bandwidth of the emission spectrum at an intensity level that is −20 dB lower than the maximum intensity is defined as the SC band, the SC band is 100 nm or more. Further, the flatness of the spectrum of the emitted light within the wavelength band of the peak wavelength λ0 ± 50 nm, that is, the difference between the maximum value and the minimum value of the emitted light intensity within this range is within 15 dB.

  When the same optical pulse was incident on the optical fiber 360 from the opposite direction, the spectrum shown in FIG. 35 was obtained. In this case, the expansion of the spectrum of the emitted light is small and is 30 nm or less in the SC band. Of course, the flatness of the spectrum of the emitted light, that is, the difference between the maximum value and the minimum value of the emitted light intensity is greater than 15 dB. The leftmost peak is the spectrum of noise light.

  In addition, when the same optical pulse as the optical pulse in FIG. 34 is input to an optical fiber having the chromatic dispersion characteristic shown in FIG. 36 and the dispersion D being constant in the length direction, a spectrum as shown in FIG. 37 is obtained. It was. The length L of this optical fiber is 1 km, and the flatness of this spectrum is greater than 15 dB. The leftmost peak is the spectrum of noise light.

Next, the SC light will be described. FIG. 38 shows a spectrum of output light from the optical fiber 310 shown in FIG. 1 having the chromatic dispersion characteristics shown in FIG. 31 and the dispersion D decreasing linearly along the length direction L. The dispersion slope D _SLOP of this optical fiber is 0.03 [ps / nm ² / km], and the dispersion D decreases from 3 to −2 [ps / nm / km]. The full width at half maximum of this spectrum is 160 nm, and the flatness of the spectrum of the emitted light within the wavelength band of the peak wavelength λ0 ± 50 nm, that is, the difference between the maximum value and the minimum value of the emitted light intensity is within 15 dB. Therefore, the SC light is light having a spectral flatness within 15 dB in the wavelength band of the peak wavelength λ0 ± 50 nm and a full width at half maximum of at least 30 nm or more, preferably 100 nm or more.

  When light was incident on the optical fiber 310 from the opposite direction, the spectrum shown in FIG. 39 was obtained. This is not SC light, and the flatness of the spectrum in the wavelength band of the peak wavelength λ0 ± 50 nm of this light is larger than 15 dB, and the full width at half maximum is smaller than 30 nm.

FIG. 40 is a cross-sectional view of the optical fiber 310. The optical fiber 310 includes a core 310x, an inner clad 310 _IC that surrounds the core 310x, and an outer clad 310 _OC that surrounds the inner clad 310 _IC . The diameter DC of the core 310 decreases linearly along the length direction (light propagation direction), and the diameter D _IC of the inner cladding 310 _IC decreases linearly along the length direction. The diameter D _{OC of} 310 _OC decreases linearly along the length direction.

In order to produce a non-linear optical effect, it is preferable that the amount of fluctuation (D _OC / km) in the length direction of the outer diameter D _OC per km of the optical fiber 310 is 2 μm / km or more. The length direction variation ratio _(D C _{/ D OC)} diameter _{D C} of the core to the outer diameter _{D OC} per 1km of fiber _{310 ((D C / D OC} ) / km) is 0.5 % / Km or more is preferable. The average outer diameter per 1 m of the optical fiber may include a portion that is increased or decreased by 2 μm or more in the longitudinal direction. Moreover, it is good also as including the part which the ratio of the diameter of the core with respect to the outer diameter of an optical fiber increased or decreased by 0.005 or more in the length direction.

41 shows the refractive index distribution in the radial direction of the optical fiber shown in FIG. The relative refractive index difference Δ + (= (nc−n _OC ) / n _OC ) between the core 310x and the outer cladding 310 _OC is 1.2%, and the relative refractive index difference Δ − (= between the inner cladding 310 _IC and the outer cladding 310 _OC. (N _IC −n _OC ) / n _OC ) is −0.6%. Here, nc is the refractive index of the core 310x, n _IC is the refractive index of the inner cladding 310IC, and n _OC is the refractive index of the outer cladding. Further, the nonlinear refractive index n ₂ is 3.8 × 10 ⁻¹⁶ (cm ² / W), and the mode field diameter MFD is 5.2 μm.

FIG. 42 shows a light source system using the light source device. The light source 100 is an optical fiber ring laser and generates 1.55 μm band pulsed light. The light source 100 and the optical fiber amplifier 200 are connected by an optical fiber OP1. The optical fiber amplifier 200 is an erbium-doped fiber amplifier. The pulsed light in the 1.55 μm band emitted from the optical fiber amplifier 200 is input to any one of the SC light generating optical fibers F via the optical fiber OP2. The optical fiber F outputs SC light. The SC light output from the optical fiber F is input to the optical demultiplexer DM via the optical fiber OP3. The SC light includes components of wavelengths λ1, λ2, and λ3. The optical demultiplexer DM is disposed in the housing HS, the input port P _IN attached to the housing HS, the first output port P1, the second output port P2, the third output port P3, and the housing HS. And a plurality of optical filters F1, F2, F3, F4, and F5. The optical filters F1, F2, F3, F4, and F5 are dichroic mirrors. The optical demultiplexer DM has a plurality of lenses (not shown) inside.

  The optical filter F1 transmits light of wavelength λ1, and reflects light of wavelengths λ2 and λ3. The optical filter F2 reflects at least light of wavelengths λ2 and λ3. The optical filter F3 transmits light having the wavelength λ2 and reflects light having the wavelength λ3. The optical filter F4 reflects at least light having the wavelength λ3. The light of wavelength λ1 that has passed through the optical filter F1 is input to the output port P1 and output through the optical fiber OP4. The light of wavelength λ2 that has passed through the optical filter F3 is input to the output port P2 and output through the optical fiber OP5. The light of wavelength λ3 reflected by the optical filter F4 is input to the output port P3 and output through the optical fiber OP6.

  The optical fiber F in which the dispersion D is reduced in the light traveling direction can be used not only for the generation of SC light but also for the generation of idler light.

  FIG. 43 shows a light source device that generates idler light. This apparatus includes a light source 100 that emits pumping light (pump light) in a 1.55 μm band, an erbium-doped optical fiber amplifier 200 that is connected by an optical fiber OP1 and amplifies the pumping light, pumping light, and a plurality of signal lights λ10. And λ20 are input through the optical fiber OP7, the optical multiplexer WDM, the optical fiber OP8 and the optical fiber F into which the light combined by the optical multiplexer WDM is input, and the light emitted from the optical fiber F And an input optical fiber OP9.

The peak power of the pump light lambda _P is weak enough not the SC light by excitation light lambda _P itself passes through the optical fiber F. A plurality of signal lights λ10 and λ20 are input to the optical multiplexer WDM via the optical fiber OP7.

FIG. 44 shows the relationship between the pumping light λ _P , the signal light λ ₁₀ , λ ₂₀ and the outgoing light λ _{10 ′} , λ _{20 ′} input to the optical fiber and the light intensity. When the signal light λ ₁₀ is input to the optical fiber F, light having a wavelength symmetrical to the wavelength λ _{P of the} excitation light, idler light λ _{10 ′} (= λ _P − (λ ₁₀ −λ _P )). It is generated in the optical fiber F and emitted. When the signal light λ ₂₀ is input to the optical fiber F, light having a wavelength symmetrical to the wavelength λ _{P of the} excitation light, idler light λ _{20 ′} (= λ _P − (λ ₂₀ −λ _P )). It is generated in the optical fiber F and emitted. That is, idler light having wavelengths λ _{10 ′} and λ _{20 ′} has a phase conjugate relationship with signal light having wavelengths λ ₁₀ and λ ₂₀ . Here, it is considered that idler light is generated by four-wave mixing. Note that the dispersion D of the optical fiber F decreases along the length direction. Therefore, when the dispersion slope is positive, the zero dispersion wavelength λ0 increases along the length direction. The wavelength λ _{P of the} excitation light emitted from the excitation light source 100 can be changed. Therefore, by changing the wavelength λ _P without changing the wavelengths of the signal light λ ₁₀ and λ ₂₀ , the wavelengths of the idler light λ _{10 ′} and λ _{20 ′} can be changed, and the power of the idler light at that time suddenly increases. It can be avoided to become smaller.

45 to 51 are graphs showing the relationship between the wavelength λ _P (nm) of the excitation light and the intensity (power) of the idler light λ _{10 ′} (or λ _{20 ′} ). The incident powers of the excitation light and the signal light are each 10 dBm.

FIG. 45 shows the wavelength λ of the excitation light when the wavelength λ _P of the excitation light is varied while the wavelength difference Δλ between the wavelength λ _P (nm) of the excitation light and the wavelength λ ₁₀ (nm) of the signal light is 5 nm. The relationship between _P (nm) and the intensity (dBm) of idler light λ _{10 ′} is shown. The zero dispersion wavelength λ ₀ of the optical fiber F having a length of 1 km is constant along the length direction and is 1550 nm. In this case, when the wavelength λ _{P of the} excitation light coincides with the zero dispersion wavelength λ ₀ , the intensity of the high idler light λ _{10 ′} is obtained, but the output power of the idler light when λ _P is near 1539 nm or 1561 nm. It can be seen that the valley of efficiency appears, with a sharp decrease.

Figure 46 is a wavelength difference △ lambda of the wavelength lambda _P of the pumping light _(nm) and the signal light wavelength lambda ₁₀ of _(nm) and 5 nm, the wavelength lambda _P of the pumping light in the case of varying the wavelength lambda _P of the pumping light The relationship between (nm) and the intensity (dBm) of idler light λ _{10 ′} is shown. The zero-dispersion wavelength λ ₀ of the optical fiber F having a length of 1 km varies linearly between 1545 nm and 1555 nm along the length direction. In this case, as described above, when the wavelength λ _P of the excitation light coincides with the zero dispersion wavelength λ ₀ , high intensity of the idler light λ _{10 ′} is obtained. However, the idler light when the λ _P is changed is obtained. The change in output power is small.

Figure 47 is a wavelength difference △ lambda of the wavelength lambda _P of the pumping light _(nm) and the signal light wavelength lambda ₁₀ of _(nm) and 5 nm, the wavelength lambda _P of the pumping light in the case of varying the wavelength lambda _P of the pumping light The relationship between (nm) and the intensity (dBm) of idler light λ _{10 ′} is shown. The zero-dispersion wavelength λ ₀ of the optical fiber F having a length of 1 km varies linearly between 1535 nm and 1565 nm along the length direction. In this case, as described above, when the wavelength λ _P of the excitation light coincides with the zero dispersion wavelength λ ₀ , high intensity of the idler light λ _{10 ′} is obtained, but λ _P is the change in the output power of the idler light. Is smaller than the above, and it can be seen that the fiber is less dependent on λ _P , that is, it can be used in a wide band.

FIG. 48 shows the relationship between the wavelength λ _P (nm) of the excitation light and the intensity (dBm) of the idler light λ _{10 ′} when the wavelength λ ₁₀ (nm) of the signal light is 1560 nm and the wavelength λ _P of the excitation light is varied. Show the relationship. The zero dispersion wavelength λ ₀ of the optical fiber F having a length of 1 km is constant along the length direction and is 1550 nm. In this case, when the wavelength λ _{P of the} excitation light coincides with the zero dispersion wavelength λ ₀ or is close to λ ₀ , high intensity of the idler light λ _{10 ′} is obtained. However, when λ _P is shorter than λ ₀ , the intensity of idler light decreases rapidly.

FIG. 49 shows the relationship between the excitation light wavelength λ _P (nm) and the intensity (dBm) of the idler light λ _{10 ′} when the wavelength λ ₁₀ (nm) of the signal light is 1560 nm and the wavelength λ _P of the excitation light is varied. Show the relationship. The zero dispersion wavelength λ ₀ of the optical fiber F having a length of 1 km varies linearly between 1542 nm and 1552 nm along the length direction. In this case, high idler light λ _{10 ′} is obtained when the wavelength λ _{P of the} excitation light is within the range of the zero dispersion wavelength λ ₀ and when the wavelength λ _{10 of the} signal light is within 5 nm. However, unlike the above condition, the intensity of idler light does not decrease so much even when λ _P becomes shorter than 1550 nm. It has also been confirmed that a high idler light λ _{10 ′} intensity can be obtained if the zero dispersion wavelength λ ₀ changes linearly by 5 nm or more in the length direction.

FIG. 50 shows the relationship between the wavelength λ _P (nm) of the excitation light and the intensity (dBm) of the idler light λ _{10 ′} when the wavelength λ ₁₀ (nm) of the signal light is 1560 nm and the wavelength λ _P of the excitation light is varied. Show the relationship. The zero-dispersion wavelength λ ₀ of the optical fiber F having a length of 1 km varies linearly between 1545 nm and 1555 nm along the length direction. In this case, a substantially uniform intensity of idler light λ _{10 ′} is obtained within a wavelength range of 1545 nm to 1560 nm. This means that even if the lambda _p variable does not change the output power of the idler light, to have any of the wavelength of the idler light, that is, the wide band can be realized.

FIG. 51 shows the relationship between the wavelength λ _P (nm) of the excitation light and the intensity (dBm) of the idler light λ _{10 ′} when the wavelength λ ₁₀ (nm) of the signal light is 1560 nm and the wavelength λ _P of the excitation light is varied. Show the relationship. The zero-dispersion wavelength λ ₀ of the optical fiber F having a length of 1 km varies linearly between 1547 nm and 1557 nm along the length direction. In this case, in this case, a substantially uniform intensity of the idler light λ _{10 ′} is obtained within the wavelength range of 1550 nm to 1560 nm, and a broad band can be achieved as in the case of FIG.

In order to efficiently generate idler light, it is desirable that the wavelength λ _{P of the} excitation light coincides with the zero dispersion wavelength λ ₀ . The zero dispersion wavelength λ ₀ of the present optical fiber F is different in the longitudinal direction, and the range thereof includes the wavelength λ _{P of the} pumping light. The wavelength λ _{P of the} pumping light coincides with a predetermined zero dispersion wavelength λ _{0 at} a predetermined position in the longitudinal direction of the optical fiber F. Therefore, the present optical fiber F can efficiently generate idler light λ _{10 ′} and λ _{20 ′} regardless of the wavelength λ _{P of the} excitation light. In order to efficiently generate idler light, the absolute value of the dispersion slope D _SLOP within the wavelength band of the signal light of the optical fiber F is preferably 0.04 [ps / nm ² / km] or less. Further, it is preferable that the dispersion D within the wavelength band of the signal light includes a region that decreases or increases in the length direction of the fiber F.

In addition, when the nonlinear refractive index of the optical fiber F is n ₂ , the effective core area is A _eff , and the peak power of the excitation light λ _P is P _peak , in order to produce a nonlinear optical effect, n ₂ ≧ 3.2 × 10 ⁻²⁰ (m ² / W), A _eff ≦ 50 × 10 ⁻¹² (m ² ), P _peak ≧ 10 × 10 ⁻³ (W), and therefore (n ₂ / A _eff ) It is preferable that × P _peak ≧ 6.4 × 10 ⁻¹² . In order to produce a nonlinear optical effect, it is more preferable that n ₂ ≧ 4 × 10 ⁻²⁰ (m ² / W). Further, in order to produce a nonlinear optical effect, the relative refractive index difference Δ + (= (nc−n _OC ) / n _OC ) between the core 310x and the outer cladding 310 _OC shown in FIG. The relative refractive index difference Δ + (= (n _OC −n _IC ) / n _OC ) between the inner cladding 310 _IC and the outer cladding 310 _OC is preferably −0.6% or less. In this example, the refractive index n _OC of the outer cladding 310 _{OC is} the refractive index of quartz.

  The present invention is not limited to the above-described embodiments and examples, and can be modified. For example, the mode of chromatic dispersion reduction may be exponential or the like, and the specific mode of the optical fiber for generating SC light is not limited to the numerical mode of the above embodiment.

  As described above, the optical fiber according to the present invention is an optical fiber that outputs nonlinear phenomenon light in response to input pulsed light of a predetermined wavelength, and the main generation region of the nonlinear phenomenon light is the pulsed light. It is characterized by having a dispersion decreasing region in which the chromatic dispersion decreases from a positive value as it progresses. Nonlinear phenomenon light is light generated by a nonlinear phenomenon such as supercontinuum light or idler light. When the optical fiber includes the dispersion reduction region, the nonlinear phenomenon light is efficiently generated in a wide band.

In the dispersion reduction region, super continuum light is more efficiently generated when the chromatic dispersion is reduced from a positive value to a negative value along with the traveling direction of the pulsed light. An optical fiber that inputs pump light having a wavelength different from that of signal light and generates nonlinear phenomenon light in a predetermined wavelength region, and an absolute value of a dispersion slope in the signal light wavelength band is 0.04 (ps / nm ² / km), and when the zero dispersion wavelength is increased or decreased by 5 nm or more in the longitudinal direction of the optical fiber, nonlinear phenomenon light such as idler light is efficiently generated.

  This dispersion decreasing region preferably has a zero dispersion wavelength of 1.5 μm band at a predetermined position. In this case, if signal light is simultaneously introduced into the optical fiber using the input pulsed light as pumping light, nonlinear phenomenon light such as idler light can be efficiently generated.

  The dispersion decreasing region preferably includes a polarization maintaining fiber, and four-wave mixing for generating nonlinear phenomenon light is likely to occur, and the nonlinear phenomenon light can be generated more efficiently.

  In addition, in the case where the average outer diameter per 1 m of the optical fiber includes a portion where the longitudinal direction increases or decreases by 2 μm or more, or the ratio of the core diameter to the outer diameter of the optical fiber increases by 0.005 or more In the case where the reduced portion is included, nonlinear phenomenon light can be generated efficiently.

  Further, for the generation of nonlinear phenomenon light, the dispersion reducing region may include a core and a clad surrounding the core, and the core diameter and the diameter of the clad both include a portion that decreases along the longitudinal direction. Desirably, the relative refractive index difference with respect to quartz of the core is + 1.2% or more, and the relative refractive index difference with respect to quartz in the vicinity of the core of the clad is preferably −0.6% or less.

Further, in order to generate nonlinear phenomenon light, the dispersion slope in the predetermined wavelength region of the dispersion decreasing region is −0.1 (ps / nm ² / km) or more and 0.1 (ps / nm ² / km). The following is desirable.

When the absolute value of the dispersion slope in the predetermined wavelength region of the dispersion decreasing region is 0.04 (ps / nm ² / km) or less, nonlinear phenomenon light such as idler light can be efficiently generated. it can.

In order to generate nonlinear phenomenon light, the peak power P _{peak of} the pulse light, the nonlinear refractive index n ₂ of the dispersion decreasing region, and the effective core area A _eff are (n ₂ / A _eff ) · P _peak > 4 It is desirable to satisfy the relationship of 5 × 10 ⁻¹⁰ .

Further, the peak power Ppeak of the pulsed light, the nonlinear refractive index n ₂ in the dispersion decreasing region, and the effective core area A _eff satisfy the relationship of (n ₂ / A _eff ) · P _peak > 6.4 × 10 ^−12. It is further desirable.

In this case, in particular, if the nonlinear refractive index n ₂ is 4 × 10 ⁻²⁰ (m ² / W) or more, nonlinear phenomenon light can be generated more preferably.

  The light source device of the present invention includes the optical fiber and a light source that is optically coupled to one end of the optical fiber and emits pulsed light.

  The light source system of the present invention includes the optical fiber, a light source that is optically coupled to one end of the optical fiber to emit pulsed light, and an optical demultiplexer that is optically coupled to the other end of the optical fiber. It is characterized by that. The pulsed light emitted from the light source enters the optical fiber and is output as nonlinear phenomenon light such as supercontinuum light in a wide wavelength range, but this is separated for each wavelength by the optical demultiplexer, and wavelength multiplexed communication Can be used.

  The light source system of the present invention includes the optical fiber, a light source that optically couples to one end of the optical fiber and emits pulsed light, and an optical multiplexer that couples a plurality of signal lights together with the pulsed light to one end of the fiber. It is provided with. Since the plurality of signal lights are input to the optical fiber together with the excitation light by the optical multiplexer, a plurality of idler lights can be generated.

Further, in a light source device including a light source that generates excitation light and an optical fiber that receives the excitation light and the signal light and emits nonlinear phenomenon light, the absolute value of the dispersion slope of the optical fiber in the wavelength band of the signal light is 0.04 (ps / nm ² / km) or less, and when the zero dispersion wavelength of the optical fiber changes along the longitudinal direction of the optical fiber within a predetermined wavelength range including the wavelength of the pumping light, Generation of nonlinear phenomenon light such as idler light can be performed. In the present invention, since the zero-dispersion wavelength can be made to coincide with any point of the optical fiber regardless of the wavelength of the excitation light, nonlinear phenomenon light such as idler light can be generated efficiently. it can. In particular, when the wavelength of the pumping light is variable, the idler light has a wavelength at a position symmetrical to the signal light. Therefore, changing the wavelength of the pumping light does not change the wavelength of the signal light. The wavelength of light can be changed.

  The following is a description of the possible principle of occurrence of the above phenomenon. That is, in the optical fiber, when high peak pulse light is input to the dispersion decreasing region, the refractive index felt by the light is changed by the optical Kerr effect, and self-phase modulation of the light wave occurs. As a result, in the wavelength distribution of light in the optical fiber, a negative chirp is generated with a long wavelength at the rising edge of the pulsed light and a short wavelength at the falling edge of the pulsed light. At least initially, the light input to the dispersion decreasing region travels in the anomalous dispersion region. Therefore, in the anomalous dispersion region in which the longer wavelength has the slower group velocity, the generation of wavelength distribution and the pulse compression proceed simultaneously.

  If the dispersion is reduced in the longitudinal direction, the compression is performed more efficiently and the pulse peak power is increased. However, the nonlinear phenomenon is more likely to occur, and the spectrum is broadened.

  Thus, light having a wide wavelength range can be obtained by self-phase modulation of the optical Kerr effect, four-wave mixing, etc., and supercontinuum light is obtained. In order to promote efficient four-wave mixing, it is necessary for light of different wavelengths to be present and interact at approximately the same time and at the same position. It is desirable that the difference in group velocity between light is small.

  In an optical fiber having a dispersion-decreasing region that starts with anomalous dispersion and decreases chromatic dispersion in the direction in which the light should travel, in the dispersion-decreasing region that is the main part of supercontinuum light generation, Supercontinuum light is generated by light wave mixing.

  Then, when the chromatic dispersion changes in the light traveling direction, a kind of scanning with a zero dispersion wavelength is performed in the vicinity of the wavelength of the light where the four-wave mixing occurs. Mixing is likely to occur, and light having a wide wavelength range is generated. As a result, supercontinuum light in a wide wavelength range is generated.

  It should be noted that the parts other than the dispersion reduction region have a small absolute value of dispersion in the wavelength range of supercontinuum light, and the use of a dispersion flat fiber having a small absolute value of dispersion slope means that four-wave mixing and supercontinuity are possible. This is desirable because the interaction length of light of each wavelength contained in the nium light becomes long.

  The dispersion decreasing region may include a plurality of optical fibers having different wavelength dispersions, and the plurality of optical fibers may be cascaded in the longitudinal direction.

  Since an optical fiber is configured by cascading a plurality of optical fibers having different wavelength dispersions in the longitudinal direction, the optical fiber can be easily manufactured.

  In the above optical fiber, (i) a first optical fiber having a first average chromatic dispersion value which is a positive value, and (ii) a second average chromatic dispersion smaller than the first average chromatic dispersion value. A second optical fiber having a value and having an end surface to which light is incident connected to an end surface from which light is emitted from the first optical fiber. In this optical fiber, the chromatic dispersion decreasing change in the traveling direction of light becomes discrete, but it acts in the same manner as described above for the occurrence of self-phase modulation, four-wave mixing and the like. In this optical fiber, an optical fiber having an appropriate chromatic dispersion value may be cascaded downstream of the second optical fiber on the condition that the chromatic dispersion does not increase in the light traveling direction. Good.

At each position of the dispersion decreasing area, dispersion slope relates to wavelength of the generated wavelength range of supercontinuum ^light, is ^{-0.1 [ps / nm 2 /km]~0.1[ps/nm 2} / km] In this case, the dispersion difference between wavelengths at each position in the dispersion reduction region is small. Therefore, the optical Kerr effect, which is a nonlinear optical effect, can be efficiently expressed, and supercontinuum light in a wide wavelength range can be generated.

Further, from the viewpoint of generating supercontinuum light in a wide wavelength range, the absolute value of the dispersion slope is preferably as small as possible. For example, the dispersion slope ^value, it is preferable to use a dispersion flattened fiber to be ^{-0.04 [ps / nm 2 /km]~0.04[ps/nm 2} / km].

  Regarding the dispersion slope, the absolute value is a problem. If the absolute values are the same, the contribution of the supercontinuum light to the wavelength width does not change much even if the signs of the values are different.

  In the dispersion decreasing region, the dispersion slope changes from a positive value to a negative value, or from a negative value to a positive value, for example, in the direction in which the light should travel, than when the dispersion slope is constant. When the group delay difference is reduced, by changing the dispersion slope in the dispersion reduction region to such an extent that the polarity changes in the traveling direction of light, the group delay in the dispersion reduction region is larger than when the dispersion slope is constant. The difference can be reduced. As a result, the overlap in the time domain of light of each wavelength increases, and supercontinuum light can be generated efficiently.

  When the dispersion decreasing region has a zero dispersion wavelength in the 1.5 μm band, the following advantages are obtained. In recent years, when an optical fiber mainly made of quartz glass is used, light having a wavelength of 1.5 μm band with low transmission loss is often used as light propagating through the optical fiber. Therefore, from the viewpoint of preventing waveform distortion due to wavelength dispersion, an optical fiber having a zero dispersion wavelength in the 1.5 μm band is used as the optical fiber. In this case, since it has a zero dispersion wavelength in the 1.5 μm band, the influence of chromatic dispersion is reduced for the supercontinuum light component having a wavelength of 1.5 μm band, and a suitable supercontinuum light output is obtained. be able to. When generating SC light in the 1.3 μm band, it is preferable to set the zero dispersion wavelength to a wavelength of 1.3 μm band.

  Furthermore, it is also possible to generate SC light in the 1.3 μm band and 1.5 μm band by setting the zero dispersion wavelength to a wavelength of 1.3 μm band or 1.5 μm band.

  When the dispersion reduction region has polarization maintaining characteristics, the following advantages are obtained. The degree of expression of the nonlinear optical effect depends on the composition of the medium material and the direction of the polarization plane of the propagating light. Therefore, when the dispersion-decreasing region has polarization maintaining characteristics in this way, the same nonlinear optical effect appears when light pulses are input at the same time under the same conditions, and stable supercontinuum light is generated. Is done. As for four-wave mixing, four-wave mixing occurs best when two interacting lights have the same polarization plane direction. Therefore, in this optical fiber, the plane of polarization is maintained in the process of generating supercontinuum light, so that the light of each wavelength generated by self-phase modulation and four-wave mixing has the same polarization plane direction and is efficient. Super continuum light can be generated.

In the dispersion reduction region, (n ₂ / A _eff ) · P _peak > 0.03 × 10 ⁻⁸ between the nonlinear refractive index n ₂ , the effective core area A _eff and the peak power P _peak of the incident pulsed light. When the relationship of [1 / W] × 1.5 [W] = 0.045 × 10 ⁻⁸ holds, the following advantages are obtained. The refractive index n is a function of the power level P of the input light, and n (P) = n ₀ + (n ₂ / A _eff ) · P (2), where n ₀ : 0th-order refractive index. ,It can be expressed as. As (n ₂ / A _eff ) · P is larger, the nonlinear optical effect is more pronounced, and supercontinuum light is efficiently generated. If the power level P of the input light is the same, the greater the (n ₂ / A _eff ), the more the nonlinear optical effect is manifested, and supercontinuum light is efficiently generated.

In this optical fiber, since (n ₂ / A _eff ) · P _peak > 0.045 × 10 ⁻⁸ , SC light is efficiently generated with a wavelength width of several tens of nm or more. Note that the peak power level P _peak easily obtained when a normal semiconductor laser and an optical fiber amplifier are used is about 1.5 [W], so that (n ₂ / A _eff )> 0.03 [1 / W], SC light is efficiently generated with a wavelength width of several tens of nm or more.

  The light source device receives (a) pulsed light generating means for generating high-peak pulsed light having a predetermined wavelength and (b) high-peak pulsed light generated by the pulsed light generating means to generate super-continuum light. And the above optical fiber. In this light source device, the pulsed light generating means generates high peak pulsed light having a predetermined wavelength and inputs the generated high peak pulsed light to the optical fiber. When high peak pulse light is input to the optical fiber and travels, as described above, supercontinuum light is generated and output as the output of the light source.

  The pulse light generation means includes (i) a pulse light generator that generates short pulse light, and (ii) an optical amplifier that inputs, amplifies and outputs the short pulse light output from the pulse light generator. It may be. In this case, in the generation of the high peak pulse light, the short pulse light generated by the pulse light generator is amplified by the optical amplifier to obtain the high peak pulse light. Therefore, it is not necessary to generate high peak pulse light, and a light source that easily outputs supercontinuum light can be realized. The optical fiber is effective not only for supercontinuum light but also for generation of idler light.

  INDUSTRIAL APPLICABILITY The present invention can be used for an optical fiber and a light source device that emit nonlinear phenomenon light such as supercontinuum light or idler light generated based on a nonlinear optical effect caused by incidence of an optical pulse with high peak power.

The block diagram of the light source device of 1st Embodiment. Explanatory drawing of the optical fiber 310 used in 1st Embodiment. The graph which shows the relationship between the value of ratio of nonlinear refractive index and effective core area, and the wavelength width of SC light. 1 is a configuration diagram of a light source device according to Embodiment 1. FIG. 3 is a graph showing spectra of high peak pulse light and generated SC light in the light source device of Example 1. FIG. 6 is a configuration diagram of a light source device according to a second embodiment. 6 is a graph showing a spectrum of SC light generated by the light source device of Example 2. FIG. 6 is a configuration diagram of a light source device according to a third embodiment. 10 is a graph showing a spectrum of SC light generated by the light source device of Example 3. FIG. 6 is a configuration diagram of a light source device according to a fourth embodiment. 6 is a graph showing a spectrum of SC light generated by the light source device of Example 4. 6 is a graph showing a spectrum of SC light generated by the light source device of Example 4. FIG. 6 is a configuration diagram of a light source device according to a fifth embodiment. 10 is a graph showing a spectrum of SC light generated by the light source device of Example 5. The block diagram of the light source device of 2nd Embodiment. The block diagram of the optical fiber 320 used by 2nd Embodiment. FIG. 10 is a configuration diagram of a light source device according to a sixth embodiment. 10 is a graph showing a spectrum of SC light generated by the light source device of Example 6. The block diagram of the light source device of 3rd Embodiment. The block diagram of the optical fiber 320 used in 3rd Embodiment. FIG. 10 is a configuration diagram of a light source device according to a seventh embodiment. 10 is a graph showing a spectrum of SC light generated by the light source device of Example 7. The block diagram of the light source device of 4th Embodiment. The block diagram of the optical fiber 320 used in 4th Embodiment. FIG. 10 is a configuration diagram of a light source device according to an eighth embodiment. 10 is a graph showing a spectrum of SC light generated by the light source device of Example 8. The block diagram of the light source device of 5th Embodiment. The block diagram of the optical fiber 320 used in 5th Embodiment. FIG. 10 is a configuration diagram of a light source device according to a ninth embodiment. 10 is a graph showing a spectrum of SC light generated by the light source device of Example 9. The graph which shows the relationship between wavelength (lambda) (nm) and wavelength dispersion D. FIG. The graph which shows the relationship between wavelength (lambda) (nm) and wavelength dispersion D. FIG. The block diagram of the light source device of 6th Embodiment. The graph which shows the relationship between wavelength (lambda) (nm) and light intensity (dBm). The graph which shows the relationship between wavelength (lambda) (nm) and light intensity (dBm). The graph which shows the relationship between wavelength (lambda) (nm) and chromatic dispersion (ps / km / nm). The graph which shows the relationship between wavelength (lambda) (nm) and light intensity (dBm). The graph which shows the relationship between wavelength (lambda) (nm) and light intensity (dBm). The graph which shows the relationship between wavelength (lambda) (nm) and light intensity (dBm). Sectional drawing of an optical fiber. The figure which shows refractive index distribution along an optical fiber diameter. The block diagram of the system using SC light source device. The block diagram of the system using an idler light source device. The graph which shows the relationship between wavelength (lambda) (nm) and light intensity. The graph which shows the relationship between wavelength (lambda) (nm) and light intensity (dBm). The graph which shows the relationship between wavelength (lambda) (nm) and light intensity (dBm). The graph which shows the relationship between wavelength (lambda) (nm) and light intensity (dBm). The graph which shows the relationship between wavelength (lambda) (nm) and light intensity (dBm). The graph which shows the relationship between wavelength (lambda) (nm) and light intensity (dBm). The graph which shows the relationship between wavelength (lambda) (nm) and light intensity (dBm). The graph which shows the relationship between wavelength (lambda) (nm) and light intensity (dBm).

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Pulse generator, 200 ... Optical amplifier, 310, 320, 330, 340, 350 ... Optical fiber, 341,342,351,352,353 ... Optical fiber.

Claims (10)

An optical fiber that inputs pump light having a wavelength different from that of signal light and generates non-linear phenomenon light that is idler light in a predetermined wavelength region, and has an absolute value of a dispersion slope of 0.04 (ps) in the signal light wavelength band. / Nm ² / km) or less, and the zero dispersion wavelength is increased or decreased by 5 nm or more in the longitudinal direction of the optical fiber.   2. The optical fiber according to claim 1, wherein chromatic dispersion decreases from a positive value to a negative value as the pulsed light travels in a dispersion decreasing region provided in a main generation region of the nonlinear phenomenon light. .   The optical fiber according to claim 2, wherein the dispersion decreasing region has a zero dispersion wavelength of 1.5 μm band at a predetermined position.   The optical fiber according to claim 2, wherein the dispersion reduction region includes a polarization maintaining fiber.   5. The relative refractive index difference with respect to quartz of the core of the optical fiber is + 1.2% or more, and the relative refractive index difference of quartz with respect to quartz near the core is −0.6% or less. An optical fiber as described in 1. The dispersion slope in the predetermined wavelength region of the dispersion decreasing region is −0.1 (ps / nm ² / km) or more and 0.1 (ps / nm ² / km) or less. 2. The optical fiber according to 2. The peak power P _peak of the pulsed light, the nonlinear refractive index n ₂ of the dispersion decreasing region, and the effective core area A _eff satisfy the relationship of (n ₂ / A _eff ) · P _peak > 4.5 × 10 ^−10. The optical fiber according to claim 2. 3. The optical fiber according to claim 2, wherein a nonlinear refractive index n ₂ of the dispersion decreasing region is 4 × 10 ⁻²⁰ (m ² / W) or more. An optical fiber according to claim 1;
A light source for generating the pump light ;
A light source device comprising: The light source device according to claim 9, wherein the wavelength of the pump light is variable.

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