WO2008075728A1

WO2008075728A1 - Method for changing optical spectrum, and apparatus for generating light with changed spectrum

Info

Publication number: WO2008075728A1
Application number: PCT/JP2007/074458
Authority: WO
Inventors: Tomoharu Hasegawa; Tatsuo Nagashima; Seiki Ohara; Naoki Sugimoto
Original assignee: Asahi Glass Company, Limited
Priority date: 2006-12-21
Filing date: 2007-12-19
Publication date: 2008-06-26
Also published as: JP2010054522A

Abstract

This invention provides a method for changing a spectrum of optical pulses which can realize energy conversion in a C band with high efficiency with a nonquartz-type nonlinear optical fiber. The method comprises introducing optical pulses into one end of a nonlinear optical fiber and generating light with changed waveforms from the other end of the nonlinear optical fiber. The nonlinear optical fiber is formed of glass containing not less than 40% by mole of Bi2O3, and the group velocity dispersion is not more than -10ps/nm/km. There is also provided an apparatus for generating light with a changed spectrum, wherein optical pulses are introduced into one end of a nonlinear optical fiber and light with a changed spectrum are generated from the other end of the nonlinear optical fiber, the nonlinear optical fiber is formed of glass containing not less than 40% by mole of Bi2O3, and the group velocity dispersion is not more than -10ps/nm/km.

Description

Specification

Optical spectrum changing method and spectrum changing light generator

Technical field

[0001] The present invention relates to a method and a spectrally changed light generator for generating light whose spectrum has been changed from incident light (hereinafter sometimes referred to as spectrally changed light) using a nonlinear optical fiber having normal dispersion. In particular, it is suitable for compact and highly efficient generation of C-band spectrum change light.

Background art

[0002] When strong light is incident on a non-linear medium, a new frequency component is generated due to the self-phase modulation effect, and white light is generated. In particular, strong white light generation has been reported for optical fibers due to strong! /, Optical confinement and length, and working length (see Non-Patent Document 1).

However, in the generation of white light using a normal silica-based optical fiber, multiple nonlinear effects appear to overlap, so that the generated spectrum is intermittent and complex, which is not practical. The dispersion was controlled in the longitudinal direction of the optical fiber so as to efficiently cut out an arbitrary wavelength to solve this problem and generate a smooth spectrum, and a frequency shift corresponding to the dispersion was given in the incident nozzle. A method using a light source has been proposed (see Patent Document 1).

Patent Document 1: Japanese Patent Laid-Open No. 10-90737

Non Patent Literature 1 Japanese Journal of Applied Physics Vol. 40 (2001) pp.L365

Disclosure of the invention

Problems to be solved by the invention

[0004] However, the fiber whose dispersion is controlled in the longitudinal direction of the optical fiber is generally unstable, and the dispersion value of the nonlinear fiber is also unstable. In addition, the technology that imparts a frequency shift in the optical noise of about femtosecond force is also a method that is used in basic research of ultrafast spectroscopy and is not common. In addition, silica-based nonlinear fibers that are widely used have small optical nonlinearities, and it is necessary to use extremely long fibers in order to obtain sufficient nonlinear effects, or the compactness of the module is impaired, and temperature, vibration, etc. There is a problem with external disturbances!

[0005] On the other hand, a film made of a material having high nonlinearity such as BiO or lead-containing quartz glass.

twenty three

It was difficult for Aiba to obtain broadband optical nonlinearity with large group velocity dispersion. In recent years, with the development of optical communication technology, the optical technology in the C band of 1530 to 1565 nm has increased in maturity. However, as described above, it is difficult to obtain a wide-band ultrashort pulse light source that can efficiently convert energy within the C band using conventional nonlinear optical fibers and general-purpose technology.

The power of all the white light described above is spectrum change light The present invention aims to provide an optical spectrum change method and a spectrum change light generator capable of solving such problems.

Means for solving the problem

[0006] The present invention is a method of generating light having an optical noise incident on one end of a nonlinear optical fiber and generating a spectrum-changed light from the other end. The nonlinear optical fiber contains BiO at 40 mol% or less.

twenty three

Provided is an optical spectrum changing method comprising an upper glass and having a group velocity dispersion of 160 ps / nm / km or more and 1 Ops / nm / km or less.

In addition, a device that generates light with an optical node entering one end of a nonlinear optical fiber and generating a spectrum-changed light from the other end, the optical fiber containing 40 mol% or more of BiO.

twenty three

A spectrally varying light generator with a group velocity dispersion of 160ps / nm / km or more and 10ps / nm / km or less is provided.

The invention's effect

[0007] A simple configuration using a general-purpose femtosecond laser as a light source and a highly nonlinear optical fiber that achieves both high nonlinearity and small group velocity dispersion compared to conventional nonlinear optical fibers are efficient for stable operation. Infrared white femtosecond light having a flat spectrum can be obtained.

Brief Description of Drawings

FIG. 1 is a block diagram for explaining the present invention.

FIG. 2 is an example of a conceptual diagram of a transverse section of a holey fiber used in the present invention.

[Fig. 3] Scanning electron microscope (SEM) photograph of the transverse section of the holey fiber used in the present invention. It is an example.

FIG. 4 is a diagram showing a spectrum of femtosecond optical noise output from a nonlinear optical fiber. FIG. 5 is a diagram showing a flowchart of a calculation program.

[Fig. 6] A diagram showing a calculation result and a measurement result of a spectrum of femtosecond optical noise output from a nonlinear optical fiber.

FIG. 7 is a diagram showing a calculation result of a ratio of energy contained in a C band in femtosecond optical noise output from a nonlinear optical fiber. Explanation of symbols

[0009] 10: Air-clad optical fiber (holey fiber)

11: Hole

12: Optical transmission glass

13: Hollow glass fiber

14: Plate glass

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a block diagram for explaining the present invention. The present invention is not limited to FIG.

In the spectrum changing light generator shown in Fig. 1, a femtosecond pulse laser, an erbium-doped fiber amplifier (hereinafter also referred to as EDFA! /) And a nonlinear optical fiber are connected in sequence.

The femtosecond pulse laser is a general-purpose laser, and the center wavelength of the light pulse emitted from it is typically 1550 nm; 1560 nm, the pulse width is lOOfs ~; lps, the peak power is 10 W ~;

The optical node is usually transmitted after being attenuated by an attenuator (not shown) in order to suppress the occurrence of nonlinear effects in the transmission path.

[0011] An optical pulse is a pump light having a wavelength of 980 nm emitted from a pumping light source (not shown) and a coupler.

(Not shown) is combined and enters the EDFA.

The net average power of light pulses incident on a nonlinear optical fiber is about 1 OmW to 10 W It is. If it exceeds 10 W, the pulse quality may deteriorate and the spectrum shape may be destroyed due to nonlinear effects during transmission or stimulated scattering due to acoustic phonon. The peak power of the optical noise incident on the nonlinear optical fiber can be adjusted by changing the pump light input value to the EDFA.

[0012] The optical pulse amplified by the EDFA is incident on the nonlinear optical fiber, and the spectral width is expanded and converted into spectrally changed light. The amount of spectral width expansion strongly depends on the input peak power of the optical pulse. When the spectral width is expressed as 10 dB width (Δ λ), Δ λ is 50 nm when the peak power is 50 W, and 140 nm is typical when the peak power is 160 W. Is. Here, the 10 dB width is the width of the 10 dB wavelength range, that is, the wavelength range where the 10 dB intensity is weaker than the maximum value of the spectrum intensity.

[0013] When the center wavelength of the incident light pulse is 1550 nm to 1560 nm, the pulse width is 100 fs to lps, and the peak power is 0 W to 1000 W, the 10 dB wavelength range of the spectrally changing light is wider than 1 530 nm; The power of light in the wavelength range from 1530 nm to 1565 nm in the Pectonore modified fluorescence is typically 50% or more of the spectrally modified light power.

Next, the nonlinear optical fiber (hereinafter sometimes simply referred to as an optical fiber) in the present invention will be described.

The optical fiber is made of glass containing 40 mol% or more of BiO. Not like that

twenty three

Because of the lack of optical nonlinearity, there is a risk that the spectrum of the spectrum-changing light will not have a sufficient width, or there is no appropriate normal dispersion, and the instability of light propagation due to modulation instability In addition, since the spectral width of the spectrum-changing light is significantly widened, wavelength conversion into the C band may be inefficient.

[0015] As such glass, Bi O 40-75%, B

2 3 2

O 12-45%, Ga O 1-20%, In O 1-20%, ZnO 0-20%, BaO 0-

3 2 3 2 3

15%, SiO + A1 O + GeO 0—15%, MgO + CaO + SrO 0—15%, SnO +

2 2 3 2 2

TeO + TiO + ZrO + Ta O + Y O + WO 0—10%, CeO 0—5%, force, etc.

2 2 2 2 5 2 3 3 2

An example is a glass that becomes qualitative and has Ga O + In O + ZnO of 5% or more.

2 3 2 3

[0016] When the group velocity dispersion (hereinafter also referred to as GVD) of optical fibers exceeds -10 ps / nm / km, the spectrum width increases significantly, and the energy stays within the C band (wavelength range: 1530 to 1565 nm). May decrease the spectral smoothness, or may cause unstable femtosecond light propagation. Preferably, it is 20 ps / nm / km or less. In addition, if the G VD is less than −160 ps / nm / km, the spectrum expansion of the femtosecond light pulse is insufficient, and it may not be possible to generate light in the entire C band. GVD is typically over 50 ps / nm / km.

[0017] The third-order nonlinear coefficient (hereinafter also referred to as γ or nonlinear constant) for light having a wavelength of 1550 nm of the optical fiber is preferably ファイバ λν- ^ π ¹ or more. If it is less than 470W— ^ π ¹ , the fiber length will be longer if the nonlinear effect is increased, and it will be more susceptible to disturbances such as temperature fluctuations and vibrations. More preferably, it is 625 W— ^ m— ¹ or more.

[0018] The optical fiber is typically a holey fiber, for example, an air-clad fiber as shown in a conceptual cross-sectional view in FIG.

The air-clad optical fiber 10 includes six holes 11, an optical transmission glass 12, a hollow glass fiber 13, and a sheet glass 14.

The hollow portion of the hollow glass fiber 13 is composed of six holes 11 extending in the axial direction (perpendicular to the paper surface), and adjacent holes are partitioned by a sheet glass 14 existing between them. .

[0019] The number of holes 11 is not limited to six, but is preferably three or more. With two, there is a risk of insufficient light confinement in the air-clad optical fiber. The number is preferably 12 or less, more preferably 9 or less.

[0020] The optical transmission glass 12 may be made of one kind of glass, or may be made of two or more kinds of glasses whose boundaries in the cross section are concentric.

In the former case, the optical transmission glass 12 is the core of the optical fiber 10 itself.

As an example of the latter case, the light transmission glass 12 is composed of an internal high refractive index glass and a low refractive index glass surrounding it, such as one having a higher refractive index in the center. . The optical transmission glass 12 having such a structure adjusts the γ and GVD, or when the optical fiber and the silica fiber are fusion-bonded, the waveguide structure is lost or the connection loss is large. Can be prevented or suppressed.

[0021] The hollow glass fiber 13 has a plate-like glass 1 at the center of the hollow portion formed by the air holes 11. The optical transmission glass 12 is held through 4 and light is not expected to propagate through the glass.

[0022] The plate-like glass 14 holds the light transmission glass 12 at the center of the hollow portion, and the thickness thereof is preferably 0.05-1.5. If the length is less than 0 · 05 m, the glass sheet 14 may be damaged when the optical fiber 10 is cut, and the optical transmission glass 12 may not be held. Typically 0 ·; 1 m or more. If it exceeds 1.5 m, light leakage from the light transmission glass 12 to the plate glass 14 becomes so large that light confinement may be insufficient. Preferably less than 0. δ μm! ^ Deme · ο.

The holes 11 are defined by the light transmission glass 12, the hollow glass fiber 13, and the plate-like glass 14, and at least a portion in contact with the holes 11 of the light transmission glass 12 and the holes 11 of the hollow glass fiber 13. The contacting portion and the plate-like glass 14 are preferably made of glass having the same composition, or made of glass having the same composition.

The same applies to the optical transmission glass 12 in which the plate glass 14 is preferably the exemplified glass.

If the optical transmission glass 12 is not such a glass, stable thermal molding may be difficult due to different thermal properties between the glasses.

[0025] The diameter (d) of the inscribed circle in the cross section of the optical transmission glass 12 is usually 0.2 to 10 and typically 0.5 to 4 111.

The diameter (d ′) of the circumscribed circle in the cross section of the hollow portion of the hollow glass fiber 13 is preferably (l + 2 ^1/2 ) d or more. If it is less than (l + 2 ^1/2 ) d, light confinement becomes insufficient, and propagation loss may increase. More preferably 3d or more, particularly preferably 4d or more. On the other hand, d ′ is preferably 16d or less. If it exceeds 16d, the strength of the optical fiber 10 will decrease, foreign matter will easily enter the holes 11, and the glass sheet 14 may be destroyed when trying to cut the optical fiber 10. Is concerned.

The outer diameter of the hollow glass fiber 13 is preferably 125 ± 2 m when the optical fiber 10 is fused with a quartz optical fiber (SMF) standardized by ITU-T Recommendation G. 652! /, . Example

[0026] Hereinafter, the present invention will be specifically described by way of examples. However, the interpretation of the present invention is not limited to these examples. There is no limitation by example.

(Example 1)

Yarn且成force Monore ^_0/0 Display Bi O 53. 23%, BO 27. 61%, Ga O 8. 96%, In

2 3 2 3 2 3

Obtained glass that is O 1%, ZnO 4.48%, BaO 4.23%, CeO 0.5%,

2 3 2

The raw materials were mixed and mixed to prepare a 250 g mixed raw material. This compounded raw material is placed in a platinum crucible and melted by holding at 1000 ° C for 2 hours in the atmosphere, and the resulting molten glass is poured into a plate shape, and then kept at 370 ° C for 4 hours and then cooled to room temperature. Slow cooling was performed.

[0027] A glass plate having a thickness of 1 mm and a size of 20 mm x 20 mm was prepared from the glass thus obtained, and a sample plate obtained by mirror-polishing both surfaces of the glass plate was measured for refractive index with respect to light having a wavelength of 1550 nm. It was 2.111 as measured using a model 2010 prism force bra.

[0028] Further, the glass has an oblique side of 40 mm, a short side of 20 mm, and an angle between the oblique side and the short side of 60. For a sample block with a 10 mm thick right triangle prism mirror-polished on the hypotenuse and long sides, the glass material dispersion D (unit: ps / nm m) is as follows.

/ km) was calculated. That is, the wavelength (λ) of the sample block is 492˜; the refractive index n at 1710 nm is the maximum λ using a precise refractive index measuring device GMR-1 manufactured by Carneux Optical Co., Ltd.

Obtained by the small declination method. Fitting this η to the Selmeier polynomial in equation (1)

The fitting parameters ρ, ρ, ρ and ρ were determined.

1 2 3 4

η = ρ + ρ · λ / (λ — ρ) + ρ · λ (1)

λ 1 2 3 4

When D at a wavelength of 1550 nm was calculated from equation (2) using η represented by equation (1)

X m

— 7 at I70ps / nm / km.

D = -10 ¹⁵ (l / c) -d ² n / άλ ² (2)

m

[0029] The molten glass obtained in the same manner as described above was poured into a SUS310S tea cylinder mold (cylindrical mold having a bottom surface) having an inner diameter of 28 mm and a height of 120 mm, and slowly cooled to glass. Got a stick.

Six through-holes with an inner diameter of 4 mm were formed on this glass rod using an ultrasonic machine USM-3CNC manufactured by Prosonic. The central axis of these six holes was 5 mm away from the central axis of the glass rod, and the distance between adjacent holes was lmm. [0030] Using the glass rod, the air-clad nonlinear optical fiber was produced as follows. First, a rod glass having six holes formed, a diameter of 28 mm, and a length of 130 mm was redrawn at 418 ° C. to obtain a glass rod having a diameter of 3.5 mm. Next, one end of the glass rod was sealed, placed in a glass tube having an outer diameter of 15 mm and an inner diameter of 6 mm with the sealing portion down, and then the lower end of the glass tube was sealed.

The space between the glass rod and the glass tube is depressurized at 60 kPa, and the six holes of the glass rod are heated to 425 ° C while being pressurized and expanded at 30 to 40 kPa. Were simultaneously drawn to obtain a preform with a diameter of 5 mm.

[0031] This preform was drawn under the conditions of a drawing temperature of 425 ° C and a drawing speed of 6 mm / min while pressurizing the hole at 5 kPa, d was 2.8 m, d 'force was 7.3 m, A nonlinear optical fiber having a fiber diameter of 1.25 μm and a thickness of the plate glass of 0 · 25 μm was obtained (hereinafter referred to as optical fiber A).

A scanning electron microscope (SEM) photograph of a cross section of optical fiber A is shown in FIG. The inserted photo is an enlarged photo of the hollow part.

[0032] GVD of optical fiber A with respect to light having a wavelength of 1550 nm was measured by homodyne interferometry using an Agilent 8190A and found to be 20 ± 10 ps / nm / km. That is, the absolute value was 20 ± 10 ps / nm / km. By having a hollow part, the absolute value of GVD could be made significantly smaller than the material dispersion Dm calculated by the above equation (1).

In addition, the nonlinear constant γ was calculated for optical fiber A by four-wave mixing, and it was 700 soil 70W— ^ m— ¹ .

[0033] In addition, spectrum changing light was generated as follows using an optical fiber A having a length of 46 cm.

The femtosecond light output to an IMRA fiber laser (trade name: femtolite) that outputs a femtosecond optical pulse with a center wavelength of 1560 nm, a pulse width of 500 fs, an average output of 4 mW, and a repetition frequency of 48 MHz. An attenuator that attenuates the noise by 15 dB was connected.

[0034] A separately prepared excitation light source (optical output: 200 mW) for generating 980 nm excitation light and the above-mentioned The tenator was connected to a force bra, and the femtosecond light noise and the excitation light were combined by the force bra.

The force plastic was connected to the EDFA, and femtosecond light pulses were amplified up to 250W.

[0035] The optical power of the amplified femtosecond optical noise was partially lost during transmission due to the force connection loss incident on the optical fiber A or the like. Therefore, the power of the incident net femtosecond optical pulse was 120 W at maximum.

[0036] The spectrum of the femtosecond optical pulse output from the optical fiber A was measured with an optical spectrum analyzer AQ6317 manufactured by Yokogawa Electric Corporation. Figure 4 shows the spectrum measurement results. Moreover, the time waveform was measured by an autocorrelator HAC150 manufactured by Arnea.

[0037] The 10 dB wavelength range of the femtosecond optical pulse output from the optical fiber A was 1495 to 1615 nm, and the 10 dB width was 120 nm. The spectral broadening of the femtosecond light pulse incident on optical fiber A was 13 nm with a 10 dB width.

In addition, there is no change in the time waveform of the femtosecond optical noise incident on the optical fiber A and the femtosecond optical noise output from the optical fiber A, and a high-quality infrared white femtosecond noise is obtained. It was covered with force S.

In addition, 45% of the total energy in the femtosecond optical pulse output from the optical fiber A was present in the same band (hereinafter, the proportion of the energy of light in the C band in the output femtosecond optical pulse was Wavelength conversion efficiency.

[0038] When the output of the pumping light source is lowered, the spectrum of the femtosecond noise output from the optical fiber A is reduced in force S, and the wavelength conversion efficiency is increased.

When searching for conditions that maximize the wavelength conversion efficiency under conditions where the 10 dB wavelength range is wider than the C band, the wavelength conversion efficiency was obtained when the peak power of the femtosecond optical noise incident on optical fiber A was 50 W. Reached the maximum of 61%. Figure 4 shows the spectrum under these conditions.

Table 1 shows the relationship between the peak power (unit: W) and the wavelength conversion efficiency (unit:%) of the femtosecond optical pulse incident on optical fiber A. When the peak power is 83-50W, the 10dB wavelength range is wider than the C band. At 25-42W, the 10dB wavelength range stays within the C band. In this example, a highly efficient red light whose optical power in the C band is 50% or more of the total optical power. The peak power capable of generating an outer white femtosecond pulse (spectrum changing light) was 50 to 67W.

[0039] [Table 1]

[0040] (Example 2)

The numerical calculation according to the present invention was performed as described below for the case where femtosecond light having a wavelength of 1550 nm near the center of the C band was incident.

That is, using the split 'step' Fourier method, we performed a numerical calculation of the nonlinear Schrödinger equation describing the time evolution of the Norres light propagating in the nonlinear optical fiber. Here, the nonlinear Schrodinger equation is an equation (2.3.35) published by Yoshioka Shoten by G. P. Agrawar.

Figure 5 shows the flowchart of the calculation program.

[0041] GVD =-25 ps / nm / km, γ = 800 W— ^ m— ¹ , propagation loss 2 dB / m, incident panel center wavelength 1560 nm, peak power 120 W As shown in Fig. 6 together with the actual measurement result of Example 1, the calculation result closely reproduces the actual measurement result.

[0042] The wavelength conversion efficiency (energy included in the C band) when a femtosecond optical pulse with a center wavelength of 1550 nm and a pulse width of 500 fs is incident on an optical fiber having a length of 50 cm and a γ of 8 OOW— ^ nT ¹ Fig. 7 shows the calculation results for the ratio of 1).

The wavelength conversion efficiency is 50% or more when the peak power is S40W or less. However, below 20W, the 10dB wavelength range does not reach the entire C band. Therefore, in this embodiment, the peak power of the incident femtosecond pulsed light that generates a highly efficient white femtosecond optical pulse is 20W to 40W.

[0043] (Example 3)

Example 1 is GVD—a force that can be said to have changed the peak power with a constant S, and in this example, the GVD was changed with a constant peak voltage, and the same numerical calculation as in Example 2 was performed. That is, a femtosecond optical pulse with a center wavelength of 1560 nm and a peak power of 50 W, propagation loss of 2 dB / m, length of 50 cm, γ force S800W— ^ m— 丄, and GVD of 80 to 160 ps / nm / km The numerical calculation of the lOdB width (unit: nm) of the spectrally changed light when entering the optical fiber was performed in the same manner as in Example 2 using the split “step” Fourier method. The results are shown in Table 2. This femtosecond optical pulse is close to the femtosecond optical pulse of Example 1.

[Table 2]

From this numerical calculation result, when GVD is -140psZnm / km, 10dB width covers C band, but when 160V / nm / km, 10dB width does not cover C band. Recognize.

[0045] (Comparative example)

A bismuth oxide glass with a GVD of 280 ps / nm / km and a γ of 1100 W ¹ km— ¹ was prepared, and good results were obtained in Example 1. As a result, the 10 dB wavelength range was from 1531 to 1582 nm, which did not cover the C band. In addition, the pulse width of spectrum change light has increased to 3 ps or more, but such an increase in pulse width is undesirable for high-speed optical communications.

Industrial applicability

[0046] It can be used for wide-band ultrashort pulse light sources such as wavelength division multiplexing, medical observation equipment (coherent tomography, etc.), ultrafast spectroscopy, and infrared spectroscopy. It should be noted that the entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2006-344183, filed on December 21, 2006, are incorporated herein by reference. As it is incorporated.

Claims

The scope of the claims

This is a method of generating light with an optical nors incident on one end of a nonlinear optical fiber and the other end force spectrum changing. The nonlinear optical fiber contains 40 mol% or more of BiO.

twenty three

A method of changing an optical spectrum, comprising glass and having a group velocity dispersion of 160 ps / nm / km or more and 10 ps / nm / km or less.

2. The optical spectrum changing method according to claim 1, wherein the group velocity dispersion is 50 ps / nm / km or more.

3. The optical spectrum changing method according to claim ^1, wherein the third-order nonlinear coefficient for light having a wavelength of 1550 nm of the nonlinear optical fiber is 470 W— ^ π ¹ or more.

The method of changing an optical spectrum according to claim 1, 2 or 3, wherein the nonlinear optical fiber is a holey fiber.

Glass power containing 40 mol% or more of BiO

twenty three

Bi O 40-75%, B O 12-45%, Ga O 1-20%, In O 1-20%, ZnO

2 3 2 3 2 3 2 3

0—20%, BaO 0—15%, SiO + A1 O + GeO 0—15%, MgO + CaO + Sr

2 2 3 2

O 0 ~; 15%, SnO + TeO + TiO + ZrO + Ta O + Y O + WO 0 ~; 10%, C

2 2 2 2 2 5 2 3 3

eO 0—5%, force, essentially, Ga O + In O + ZnO is 5% or more

2 2 3 2 3

The optical spectrum changing method as described in ~ /!

A device that generates light whose optical spectrum is changed by the incidence of optical noise on one end of a non-linear optical fiber, and the optical fiber contains 40 mol% or more of BiO.

twenty three

Spectral light generator with group velocity dispersion of 160ps / nm / km or more and 10ps / nm / km or less.

The optical pulse has a wavelength power ^{s of} 1550 nm to 1560 nm, a non-less width of 100 fs to lps, a peak power of 0 W to 1000 W, and a femtosecond pulse laser capable of generating such an optical pulse. The spectral change light generator described.

8. The spectrum change light generator according to claim 7, further comprising an erbium-doped fiber amplifier connected between the femtosecond pulse laser and the optical fiber.