Non-polarization light source device and raman amplifier

A non-polarized light source, comprising:

• a laser light source that transmits a virtually linear polarized light beam, the virtually linearly-polarized light beam having plural mode components arranged at an interval of an almost equal angular frequency;
• and
• a polarization dispersion device that is connected to the laser light source in such a way that a first polarization axis meets a second polarization axis to form a 45° angle, and effects on the light beam output from the laser light source a polarization mode dispersion τ such that the degree of polarization determined by the following expression is less than 0.5 for a function A(ω′) of spectral form of a relative angular frequency ω′=ω−ωc of the angular frequency ω that has a mode interval angular frequency Δω and a central angular frequency ωc as criteria, the first polarization axis being the polarization axis of the polarization dispersion device and the second polarization axis being the polarization axis of the light beam output from the laser light source.
• 11 DOP = [LeftBracketingBar] 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δ ⁢ ⁢ ω ) 2 ⁢ cos ⁡ ( n · Δ ⁢ ⁢ ω · τ ) } 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δω ) 2 } [RightBracketingBar] ( 8 )

A non-polarized light source, comprising:

• a first laser light source that transmits a first virtually linearly-polarized light beam and a second laser light source that transmits a second virtually linearly-polarized light beam, the first and second virtually linearly-polarized light beams having plural mode components arranged at an interval of an almost equal angular frequency;
• a polarization combining unit that polarization-combines the a first transmitted light beam of the first laser light source and a second transmitted light beam of the second laser light source;
• and
• a polarization dispersion device that is connected to the polarization combining unit in such a way that a first polarization axis meets a second polarization axis to form a 45° angle, and effects on either the first transmitted light beam of the first laser light source or the second transmitted light of the second laser light source a polarization mode dispersion τ such that the degree of polarization determined by the following expression is less than 0.5 for a function A(ω′) of spectral form of a relative angular frequency ω′=ω−ωc of the angular frequency ω that has a mode interval angular frequency Δω and a central angular frequency ωc as criteria, the first polarization axis being the polarization axis of the polarization dispersion device and the second polarization axis being the polarization axis of the light beam output from the laser light source.
• 12 DOP = [LeftBracketingBar] 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δ ⁢ ⁢ ω ) 2 ⁢ cos ⁡ ( n · Δ ⁢ ⁢ ω · τ ) } 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δω ) 2 } [RightBracketingBar] ( 8 )

A Raman amplifier comprising:

• an optical fiber that is a Raman-amplifying medium and that carries a light signal;
• a non-polarized light source that includes a laser light source that transmits a virtually linearly-polarized light beam having plural mode components arranged at an interval of an almost equal angular frequency and a polarization dispersion device that is connected to the laser light source in such a way that a first polarization axis meets a second polarization axis to form a 45° angle and that effects on the light beam output from the laser light source a polarization mode dispersion that is not in the vicinity of (2π/Δω), where Δω is a mode interval angular frequency, the first polarization axis being the polarization axis of the polarization dispersion device and the second polarization axis being the polarization axis of the light beam output from the laser light source, the non-polarized light source generating a pump light in a wavelength band that effects a Raman gain on the light signal;
• and
• an injection unit that inputs into the optical fiber the pump light.

A Raman amplifier comprising:

• an optical fiber that is a Raman-amplifying medium and carrying a light signal;
• a non-polarized light source that includes a laser light source that transmits a virtually linearly-polarized light beam having plural mode components arranged at an interval of an almost equal angular frequency and a polarization dispersion device that is connected to the laser light source in such a way that a first polarization axis meets a second polarization axis to form a 45° angle, and effects on the light beam output from the laser light source a polarization mode dispersion τ such that the degree of polarization determined by the following expression is less than 0.5 for a function A(ω′) of spectral form of a relative angular frequency ω′=ω−ωc of the angular frequency ω that has a mode interval angular frequency Δω and a central angular frequency ωc as criteria, the first polarization axis being the polarization axis of the polarization dispersion device and the second polarization axis being the polarization axis of the light beam output from the laser light source, the non-polarized light source generating a pump light in a wavelength band that effects a Raman gain on the light signal;
• 13 DOP = [LeftBracketingBar] 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δ ⁢ ⁢ ω ) 2 ⁢ cos ⁡ ( n · Δ ⁢ ⁢ ω · τ ) } 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δω ) 2 } [RightBracketingBar] ( 8 )
• and
• an injection unit that inputs into the optical fiber the pump light.

A Raman amplifier comprising:

• an optical fiber that is a Raman-amplifying medium and that carries a light signal;
• a non-polarized light source that includes a first laser light source that transmits a first virtually linearly-polarized light beam and a second laser light source that transmits a second virtually linearly-polarized light beam, the first and second virtually linearly-polarized light beams having plural mode components arranged at an interval of an almost equal angular frequency, a polarization combining unit that polarization-combines the a first transmitted light beam of the first laser light source and a second transmitted light beam of the second laser light source, and a polarization dispersion device that is connected to the polarization combining unit in such a way that a first polarization axis meets a second polarization axis to form a 45° angle, and effects on either the first transmitted light beam of the first laser light source or the second transmitted light of the second laser light source a polarization mode dispersion τ such that the degree of polarization determined by the following expression is less than 0.5 for a function A(ω′) of spectral form of a relative angular frequency ω′=ω−ωc of the angular frequency ω that has a mode interval angular frequency Δω and a central angular frequency ωc as criteria, the first polarization axis being the polarization axis of the polarization dispersion device and the second polarization axis being the polarization axis of the light beam output from the laser light source, the non-polarized light source generating a pump light in a wavelength band that effects a Raman gain on the light signal;
• 14 DOP = [LeftBracketingBar] 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δ ⁢ ⁢ ω ) 2 ⁢ cos ⁡ ( n · Δ ⁢ ⁢ ω · τ ) } 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δω ) 2 } [RightBracketingBar] ( 8 )
• and
• an injection unit that inputs into the optical fiber the pump light.

A Raman amplifier comprising:

• a first optical fiber and a second optical fiber that are a Raman-amplifying medium and that, respectively, carry a first light signal and a second light signal;
• a first non-polarized light source and a second non-polarized light source that each includes a laser light source that transmits a virtually linearly-polarized light beam having plural mode components arranged at an interval of an almost equal angular frequency and a polarization dispersion device that is connected to the laser light source in such a way that a first polarization axis meets a second polarization axis to form a 45° angle and that effects on the light beam output from the laser light source a polarization mode dispersion that is not in the vicinity of (2π/Δω), where Δω is a mode interval angular frequency, the first polarization axis being the polarization axis of the polarization dispersion device and the second polarization axis being the polarization axis of the light beam output from the laser light source, the first non-polarized light source and the second non-polarized light source each generating a pump light in a wavelength band that effects a Raman gain on the light signal;
• a combining and separating unit that combines a first transmitted light beam of the first non-polarized light source and a second transmitted light of the second non-polarized light source, and splits a combined transmitted light beam into a first light beam and a second light beam;
• and
• a first injection unit that inputs into the first optical fiber the first light beam of the combining and separating unit, and a second injection unit that inputs into the second optical fiber the second light beam of the combining and separating unit.

A Raman amplifier comprising:

• a first optical fiber and a second optical fiber that are a Raman-amplifying medium and that, respectively, carry a first light signal and a second light signal;
• a first non-polarized light source and a second non-polarized light source that each includes a laser light source that transmits a virtually linearly-polarized light beam having plural mode components arranged at an interval of an almost equal angular frequency and a polarization dispersion device that is connected to the laser light source in such a way that a first polarization axis meets a second polarization axis to form a 45° angle, and effects on the light beam output from the laser light source a polarization mode dispersion τ such that the degree of polarization determined by the following expression is less than 0.5 for a function A(ω′) of spectral form of a relative angular frequency ω′=ω−ωc of the angular frequency o) that has a mode interval angular frequency Δω and a central angular frequency ωc as criteria, the first polarization axis being the polarization axis of the polarization dispersion device and the second polarization axis being the polarization axis of the light beam output from the laser light source,
• 15 DOP = [LeftBracketingBar] 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δ ⁢ ⁢ ω ) 2 ⁢ cos ⁡ ( n · Δ ⁢ ⁢ ω · τ ) } 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δω ) 2 } [RightBracketingBar] ( 8 )
• the first non-polarized light source and the non-polarized light source each generating a pump light in a wavelength band that effects a Raman gain on the light signal;
• a combining and separating unit that combines a first transmitted light beam of the first non-polarized light source and a second transmitted light of the second non-polarized light source, and splits a combined transmitted light beam into a first light beam and a second light beam;
• and
• a first injection unit that inputs into the first optical fiber the first light beam of the combining and separating unit, and a second injection unit that inputs into the second optical fiber the second light beam of the combining and separating unit.

A Raman amplifier comprising:

• a first optical fiber and a second optical fiber that are a Raman-amplifying medium and that, respectively, carry a first light signal and a second light signal;
• a first non-polarized light source and a second non-polarized light source that each includes a laser light source that transmits a virtually linearly-polarized light beam having plural mode components arranged at an interval of an almost equal angular frequency, a polarization combining unit that polarization-combines the a first transmitted light beam of the first laser light source and a second transmitted light beam of the second laser light source, and a polarization dispersion device that is connected to the polarization combining unit in such a way that a first polarization axis meets a second polarization axis to form a 45° angle, and effects on either the first transmitted light beam of the first laser light source or the second transmitted light of the second laser light source a polarization mode dispersion τ such that the degree of polarization determined by the following expression is less than 0.5 for a function A(ω′) of spectral form of a relative angular frequency ω′=ω−ωc of the angular frequency ω that has a mode interval angular frequency Δω and a central angular frequency ωc as criteria, the first polarization axis being the polarization axis of the polarization dispersion device and the second polarization axis being the polarization axis of the light beam output from the laser light source,
• 16 DOP = [LeftBracketingBar] 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δ ⁢ ⁢ ω ) 2 ⁢ cos ⁡ ( n · Δ ⁢ ⁢ ω · τ ) } 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δω ) 2 } [RightBracketingBar] ( 8 )
• the first non-polarized light source and the non-polarized light source each generating a pump light in a wavelength band that effects a Raman gain on the light signal;
• a combining and separating unit that combines a first transmitted light beam of the first non-polarized light source and a second transmitted light of the second non-polarized light source, and splits a combined transmitted light beam into a first light beam and a second light beam;
• and
• a first injection unit that inputs into the first optical fiber the first light beam of the combining and separating unit, and a second injection unit that inputs into the second optical fiber the second light beam of the combining and separating unit.

A Raman amplifier comprising:

• an optical fiber that is a Raman-amplifying medium and that carries a light signal;
• plural non-polarized light sources that each includes a laser light source that transmits a virtually linearly-polarized light beam having plural mode components arranged at an interval of an almost equal angular frequency and a polarization dispersion device that is connected to the laser light source in such a way that a first polarization axis meets a second polarization axis to form a 45° angle and that effects on the light beam output from the laser light source a polarization mode dispersion that is not in the vicinity of (2π/Δω), where Δω is a mode interval angular frequency, the first polarization axis being the polarization axis of the polarization dispersion device and the second polarization axis being the polarization axis of the light beam output from the laser light source, the plural non-polarized light sources generating pump lights having varying central wavelengths in a wavelength band that effects a Raman gain on a light signal;
• and
• a wavelength-combining and injection unit that wavelength-combines the transmitted light beams of the plural non-polarized light sources and inputs into the optical fiber a wavelength-combined transmitted light beam.

A Raman amplifier comprising:

• an optical fiber that is a Raman-amplifying medium and that carries a light signal;
• plural non-polarized light sources that each includes a laser light source that transmits a virtually linearly-polarized light beam having plural mode components arranged at an interval of an almost equal angular frequency and a polarization dispersion device that is connected to the laser light source in such a way that a first polarization axis meets a second polarization axis to form a 45° angle, and effects on the light beam output from the laser light source a polarization mode dispersion τ such that the degree of polarization determined by the following expression is less than 0.5 for a function A(ω′) of spectral form of a relative angular frequency ω′=ω−ωc of the angular frequency ω that has a mode interval angular frequency Δω and a central angular frequency ωc as criteria, the first polarization axis being the polarization axis of the polarization dispersion device and the second polarization axis being the polarization axis of the light beam output from the laser light source,
• 17 DOP = [LeftBracketingBar] 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δ ⁢ ⁢ ω ) 2 ⁢ cos ⁡ ( n · Δ ⁢ ⁢ ω · τ ) } 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δω ) 2 } [RightBracketingBar] ( 8 )
• the plural non-polarized light sources generating pump lights having varying central wavelengths in a wavelength band that effects a Raman gain on a light signal;
• and
• a wavelength-combining and injection unit that wavelength-combines the transmitted light beams of the plural non-polarized light sources and inputs into the optical fiber a wavelength-combined transmitted light beam.

A Raman amplifier comprising:

• an optical fiber that is a Raman-amplifying medium and that carries a light signal;
• plural non-polarized light sources that each includes a laser light source that transmits a virtually linearly-polarized light beam having plural mode components arranged at an interval of an almost equal angular frequency, a polarization combining unit that polarization-combines the a first transmitted light beam of the first laser light source and a second transmitted light beam of the second laser light source, and a polarization dispersion device that is connected to the polarization combining unit in such a way that a first polarization axis meets a second polarization axis to form a 45° angle, and effects on either the first transmitted light beam of the first laser light source or the second transmitted light of the second laser light source a polarization mode dispersion τ such that the degree of polarization determined by the following expression is less than 0.5 for a function A(ω′) of spectral form of a relative angular frequency ω′=ω−ωc of the angular frequency ω that has a mode interval angular frequency Δω and a central angular frequency ωc as criteria, the first polarization axis being the polarization axis of the polarization dispersion device and the second polarization axis being the polarization axis of the light beam output from the laser light source,
• 18 DOP = [LeftBracketingBar] 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δ ⁢ ⁢ ω ) 2 ⁢ cos ⁡ ( n · Δ ⁢ ⁢ ω · τ ) } 1 + ∑ n = 1 ∞ ⁢ { 2 ⁢ A ⁡ ( n · Δω ) 2 } [RightBracketingBar] ( 8 )
• the plural non-polarized light sources generating pump lights having varying central wavelengths in a wavelength band that effects a Raman gain on a light signal by varying their central wavelengths;
• and
• a wavelength-combining and injection unit that wavelength-combines the transmitted light beams of the plural non-polarized light sources and inputs into the optical fiber a wavelength-combined transmitted light beam.