Raman amplifier and raman amplifier adjustment method

• US 20050024712A1
• Filed: 07/02/2004
• Published: 02/03/2005
• Est. Priority Date: 08/01/2003
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Nakata, Masao, Hiraizumi, Maki, Shimano, Yoshio
• Granted Patent: US 7,554,721 B2
• Time in Patent Office: Days
• US Class Current: 359/334
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/06758 Tandem amplifiers
• CPC Class Codes: H01S 3/06766 C-band amplifiers, i.e. amplification in the range of about 1530 nm to 1560 nm
• CPC Class Codes: H01S 3/0912 Electronics or drivers for the pump source, i.e. details of drivers or circuitry specific for laser pumping laser diode drivers H01S5/042
• CPC Class Codes: H01S 3/094096 Multi-wavelength pumping
• CPC Class Codes: H01S 3/0941 of a laser diode
• CPC Class Codes: H01S 3/10015 by monitoring or controlling, e.g. attenuating, the input signal
• CPC Class Codes: H01S 3/1305 Feedback control systems
• CPC Class Codes: H01S 3/1608 erbium
• CPC Class Codes: H01S 3/302 in an optical fibre
• CPC Class Codes: H04B 10/0775 Performance monitoring and measurement of transmission parameters
• CPC Class Codes: H04B 10/2916 using Raman or Brillouin amplifiers

Abstract

A pumping unit supplies pumping light to a fiber connecting medium; a light monitoring unit detects light power of multiple-wavelength light; and a control unit controls the pumping light based on light power detected by the light monitoring unit and connecting medium information indicating optical characteristics in the connecting medium. The connecting medium information includes information indicating a fiber type of the fiber connecting medium, information indicating a length of the fiber connecting medium, an average fiber loss coefficient of the fiber connecting medium and an intra-station loss value.

Claims

1. A Raman amplifier amplifying multiple-wavelength light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a light monitoring unit detecting light power of the multiple-wavelength light; and

a control unit controlling the pumping light based on light power detected by said light monitoring unit and connecting medium information indicating optical characteristics of the connecting medium, wherein;

said connecting medium information comprises information indicating a fiber type of the fiber connecting medium, information indicating a length of the fiber connecting medium, an average fiber loss coefficient of the fiber connecting medium and an intra-station loss value.

2. A Raman amplifier amplifying multiple-wavelength light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a light monitoring unit detecting light power of the multiple-wavelength light; and

a control unit controlling the pumping light based on light power detected by said light monitoring unit and connecting medium information indicating optical characteristics of the connecting medium, wherein;

said connecting medium information comprises information indicating a fiber type of the fiber connecting medium, a loss value in the fiber connecting medium and an intra-station loss value.

3. A Raman amplifier amplifying multiple-wavelength light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a light monitoring unit detecting light power of the multiple-wavelength light;

a measuring unit measuring a Raman gain in the fiber connecting medium while changing power of the pumping light; and

a determination unit determining power of the pumping light to be supplied based on light power detected by said light monitoring unit and the Raman gain measured by said measuring unit.

4. The Raman amplifier as claimed in claim 3, wherein:

said pumping unit comprises a plurality of pumping light sources generating pumping light in mutually different wavelengths; and

said determination unit determines pumping ratio between said plurality of pumping light sources.

5. The Raman amplifier as claimed in claim 3, wherein:

said light monitoring unit detects, as light power of the multiple-wavelength light, a value obtained from subtracting a noise component from a light power value of an output from the fiber connecting medium.

6. The Raman amplifier as claimed in claim 5, wherein:

the noise component comprises ASS noise calculated based on light power of the pumping power and ASE noise corresponding an optical amplifier provided in an upstream station with respect to the fiber connecting medium.

7. The Raman amplifier as claimed in claim 3, wherein:

said measuring unit measures the Raman gain based on a difference between received light power occurring when power of the pumping light is set as a first value and received light power occurring when power of the pumping light is set as a second value.

8. The Raman amplifier as claimed in claim 7, wherein:

said first value is a value corresponding to a state in which the pumping light is stopped.

9. The Raman amplifier as claimed in claim 3, wherein:

said measuring unit measures the Raman gain sequentially while gradually increasing power of the pumping light until light power of the multiple-wavelength light reaches a predetermined value.

10. A Raman amplifier amplifying multiple-wavelength light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a light monitoring unit detecting light power of the multiple-wavelength light;

a noise measurement unit measuring ASS noise during the output of an optical amplifier provided in an upstream station with respect to the fiber connecting medium being stopped;

a deriving unit deriving a Raman gain in the fiber connecting medium based on the thus-measured ASS noise; and

a determination unit determining power of the pumping light to be supplied based on the light power detected by said light monitoring unit and the Raman gain derived by said deriving unit.

11. The Raman amplifier as claimed in claim 10, further comprising:

a request unit requesting the optical amplifier in said upstream station with respect to the fiber connecting medium to stop the output.

12. The Raman amplifier as claimed in claim 10, wherein:

said pumping unit comprises a plurality of pumping light sources generating pumping light in mutually different wavelengths; and

said determination unit determines a pumping ratio between the plurality of pumping light sources.

13. The Raman amplifier as claimed in claim 10, wherein;

said light monitoring unit detects, as light power of the multiple-wavelength light, a value obtained from subtracting a noise component from a light power value of an output the fiber connecting medium.

14. The Raman amplifier as claimed in claim 13, wherein:

the noise component comprises ASS noise measured by said noise measurement unit and an ASE noise corresponding to the optical amplifier provided in the upstream station with respect to the fiber connecting medium.

15. A Raman amplifier amplifying multiple-wavelength light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a light monitoring unit detecting light power of the multiple-wavelength light; and

a control unit controlling the pumping light based on the light power detected by said light monitoring unit, wherein;

said light monitoring unit comprises;

an ASS noise calculation unit calculating an ASS noise amount;

a correction unit correcting the ASS noise amount based on received light power from the fiber connecting medium and a total sum in peak power at respective wavelengths of the multiple-wavelength light; and

an operation unit obtaining light power of the multiple-wavelength light by subtracting the thus-corrected ASS noise amount from the received light power.

16. A Raman amplifier amplifying multiple-wavelength light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a light monitoring unit detecting light power of the multiple-wavelength light;

a control unit controlling the pumping light based on the light power detected by said light monitoring unit;

a wavelength filter extracting a predetermined wavelength component from input light;

an operation unit subtracting a noise component from the wavelength component extracted by said wavelength filter; and

a detecting unit detecting a trouble in an upstream station or the fiber connecting medium according to output of said operation unit.

17. The Raman amplifier as claimed in claim 16, wherein:

the wavelength component extracted by said wavelength filter comprises one of a plurality of light components configuring the multiple-wavelength light.

18. The Raman amplifier as claimed in claim 16, wherein:

the wavelength component extracted by said wavelength filter comprises probe light prepared other than signal light carrying a main signal.

19. A Raman amplifier adjustment method for adjusting a Raman amplifier amplifying multiple-wavelength light with the use of a fiber connecting medium, comprising the steps of:

a) detecting, as first received light power, received light power obtained when pumping light in first pumping power is supplied to the fiber connecting medium;

b) detecting, as second received light power, received light power obtained when pumping light in second pumping power is supplied to the fiber connecting medium;

c) calculating a Raman gain of the fiber connecting medium, based on the first received light power and the second received light power;

e) calculating an ASS noise amount based on the Raman gain; and

f) determining power of the pumping light to be supplied based on light power of the multiple-wavelength light thus detected and the Raman gain thus calculated.

20. A Raman amplifier adjustment method for adjusting a Raman amplifier amplifying multiple-wavelength light with the use of a fiber connecting medium, comprising the steps of:

a) measuring an ASS noise amount during output of an optical amplifier provided in an upstream station with respect to the fiber connecting medium being stopped;

b) deriving a Raman gain in the fiber connecting medium based on the thus-measured ASS noise amount; and

c) determining power of the pumping light to be supplied based on light power of the multiple-wavelength light and the Raman gain thus derived.

21. A Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a light monitoring unit detecting a received light amount;

a light measurement unit measuring the received light amount;

a noise component estimation unit estimating based on the pumping light amount, a noise component occurring in the fiber connecting medium;

a control unit controlling the pumping unit base on the received light amount detected by said light monitoring unit and the noise component estimation amount obtained by said noise amount estimation unit; and

a correcting unit comparing between the noise component estimation amount obtained by said noise component estimation unit and the noise component measurement value obtained by said light measurement unit, and correcting the noise component estimation amount based on the comparison result.

23. The Raman amplifier as claimed in claim 21, wherein:

said light measurement unit comprises a light spectrum analyzer for measuring light power at each wavelength in a wavelength band of the input light.

22. A Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a light measurement unit measuring the received light amount;

a light monitoring unit detecting a received light amount throughout the entirety of a predetermined signal light band;

a noise component estimation unit estimating, based on the pumping light amount, a noise component occurring in the fiber connecting medium;

a control unit controlling the pumping unit base on the received light amount detected by said light monitoring unit and the noise component estimation amount obtained by said noise amount estimation unit;

a signal light amount calculating unit obtaining a signal light amount by correcting the received light amount measured by said light measurement unit with the use of the noise component estimation amount obtained by the noise component estimation unit; and

a correcting unit comparing between the signal light amount obtained by said light measurement unit and the signal light amount obtained by said signal light amount calculating unit, and correcting the noise component estimation amount based on the comparison result.

24. The Raman amplifier as claimed in claim 22, wherein:

said light measurement unit comprises a light spectrum analyzer for measuring light power at each wavelength in a wavelength band of the input light.

25. A Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a noise component estimation unit estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

an extracting unit extracting a predetermined wavelength band including signal light from a received light signal, and causing a wavelength band other than said predetermined wavelength band to branch off;

a first monitoring unit detecting a light amount of a received light signal in the predetermined wavelength band extracted by said extracting unit;

a second monitoring unit detecting a light amount of the received light signal in the wavelength band other than the predetermined wavelength band having branched off by said extracting unit;

a control unit controlling said pumping unit based on the received light amounts detected by said first and second monitoring units and the noise component estimation value obtained by said noise component estimation unit;

a first signal light amount calculating unit calculating a signal light amount based on the detection result by said first monitoring unit;

a second signal light amount calculating unit calculating a signal light amount by correcting the detection result from said second monitoring unit with the use of the noise component estimation value by said noise component estimation unit; and

a correcting unit correcting the noise component estimation value by comparing between respective calculation values by said first signal light amount calculating unit and said second signal light amount calculating unit.

26. A Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a noise component estimation unit estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

an extracting unit extracting a predetermined wavelength band including signal light from a received light signal, and causing a wavelength band other than said predetermined wavelength band to branch off;

a first monitoring unit detecting a light amount of a received light signal in the predetermined wavelength band extracted by said extracting unit;

a second monitoring unit detecting a light amount of the received light signal in the wavelength band other than the predetermined wavelength band having branched by said extracting unit;

a control unit controlling said pumping unit based on the received light amounts detected by said first and second monitoring units and the noise component estimation value obtained by said noise component estimation unit;

a first signal light amount calculating unit calculating a signal light amount without correcting the detection result by said first monitoring unit with the use of the noise component estimation value by said noise component estimation unit; and

a second signal light amount calculating unit calculating a signal light amount by correcting the detection result from said second monitoring unit with the use of the noise component estimation value by said noise component estimation unit; and

a correcting unit correcting the noise component estimation value by comparing between respective calculation values by said first signal light amount calculating unit and said second signal light amount calculating unit.

27. A Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a noise component estimation unit estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

a light branching unit causing received light signal to branch off into a first light signal and a second light signal;

a band extracting unit extracting a predetermined wavelength band including a signal light through filtering said first light signal obtained from said light branching unit;

a first monitoring unit detecting a light amount of a light signal extracted by said band extracting unit;

a second monitoring unit detecting a light amount of the second light signal obtained from said light branching unit;

a control unit controlling said pumping unit based on the received light amounts detected by said first and second monitoring units and the noise component estimation value obtained by said noise component estimation unit;

a first signal light amount calculating unit calculating a signal light amount based on the detection result from said first monitoring unit;

a second signal light amount calculating unit calculating a signal light amount by correcting the detection result from said second monitoring unit with the use of the noise component estimation value by said noise component estimation unit; and

a correcting unit correcting the noise component estimation value by comparing between respective calculation values by said first signal light amount calculating unit and said second signal light amount calculating unit.

28. A Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a noise component estimation unit estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

a light branching unit causing received light signal to branch into a first light signal and a second light signal;

a band extracting unit extracting a predetermined wavelength band including a signal light through filtering said first light signal obtained from said light branching unit;

a first monitoring unit detecting a light amount of a light signal extracted by said band extracting unit;

a second monitoring unit detecting a light amount of the second light signal obtained from said light branching unit;

a control unit controlling said pumping unit based on the received light amounts detected by said first and second monitoring units and the noise component estimation value obtained by said noise component estimation unit;

a first signal light amount calculating unit calculating a signal light amount without correcting the detection result from said first monitoring unit with the use of the noise component estimation value by said noise component estimation unit;

a second signal light amount calculating unit calculating a signal light amount by correcting the detection result from said second monitoring unit with the use of the noise component estimation value by said noise component estimation unit; and

a correcting unit correcting the noise component estimation value by comparing between respective calculation values by said first signal light amount calculating unit and said second signal light amount calculating unit.

29. A Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a light monitoring unit detecting a received light amount;

a noise component estimation unit estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

a branching unit causing a predetermined wavelength part without including a signal light to branch off from the received light signal;

a control unit controlling said pumping unit based on the received light amount detected by said light monitoring unit and the noise component estimation value obtained by said noise component estimation unit;

a first monitoring unit detecting a light amount of said predetermined wavelength part of the received light signal having branched off by said branching unit; and

a correcting unit correcting the noise component estimation value by comparing between a noise component value obtained from the detection value by said first monitoring unit and the noise component estimation value obtained by said noise component estimation unit.

30. A Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a noise component estimation unit estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

a light branching unit causing a received light signal to branch off into a first light signal and a second light signal;

a band extracting unit extracting a predetermined wavelength part, not including a signal light, from a first light signal having branched off by said light branching unit, by means of filtering;

a first monitoring unit detecting a light amount of a light signal extracted by said band extracting unit;

a second monitoring unit detecting a light amount of a second light signal branched off by said light branching unit

a control unit controlling said pumping unit based on the received light amounts detected by said first and second monitoring units and the noise component estimation value obtained by said noise component estimation unit;

a correcting unit correcting the noise component estimation value by comparing between a noise component value obtained from the detection value by said monitoring unit and the noise component estimation value obtained by said noise component estimation unit.

31. A Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a noise component estimation unit estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

an extracting unit extracting a predetermined wavelength band including a signal light and causing a wavelength band other than said predetermined wavelength band to branch off;

a first monitoring unit detecting a light amount of a received light signal in said predetermined wavelength band extracted by said band extracting unit;

a second monitoring unit detecting a light amount of a received light signal in the wavelength band other than said predetermined wavelength band having branched off by said band extracting unit;

a control unit controlling said pumping unit based on the received light amounts detected by said first and second monitoring units and the noise component estimation value obtained by said noise component estimation unit;

a first signal light amount calculating unit calculating a signal light amount by correcting the detection result by said first monitoring unit with the use of the noise component estimation value obtained from said noise component estimation unit;

a second signal light amount calculating unit calculating a signal light amount by correcting the detection result from said second monitoring unit with the use of the noise component estimation value obtained by said noise component estimation unit;

a correcting unit correcting the noise component estimation value by comparing between respective calculation values by said first signal light amount calculating unit and said second signal light amount calculating unit.

32. A Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising:

a pumping unit supplying pumping light to the fiber connecting medium;

a noise component estimation unit estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

a light branching unit causing a received light signal to branch into a first light signal and a second light signal;

a band extracting unit extracting a predetermined wavelength band by means of filtering from said first light signal obtained from said branching unit;

a first monitoring unit detecting a light amount of a light signal extracted by said band extracting unit;

a second monitoring unit detecting a light amount of said second light signal obtained from said light branching unit;

a control unit controlling said pumping unit based on the received light amounts detected by said first and second monitoring units and the noise component estimation value obtained by said noise component estimation unit;

a first signal light amount calculating unit calculating a signal light amount by correcting the detection result by said first monitoring unit with the use of the noise component estimation value obtained by said noise component estimation unit;

a second signal light amount calculating unit calculating a signal light amount by correcting the detection result by said second monitoring unit with the use of the noise component estimation value obtained by said noise component estimation unit;

a correcting unit correcting the noise component estimation value by comparing between respective calculation values by said first signal light amount calculating unit and said second signal light amount calculating unit.

33. A Raman amplifier adjustment method for adjusting a Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising the steps of:

a) supplying pumping light to the fiber connecting medium;

b) detecting a received light amount;

c) measuring the received light amount;

d) estimating based on the pumping light amount, a noise component occurring in the fiber connecting medium;

e) controlling said step a) based on the received light amount detected in said step b) and the noise component estimation amount obtained in said step d); and

f) comparing between the noise component estimation amount obtained in said step d) and the noise component measurement value obtained in said step c), and correcting the noise component estimation amount based on the comparison result.

35. The Raman amplifier adjustment method as claimed in claim 33, wherein:

a light spectrum analyzer for measuring light power at each wavelength in a wavelength band of the input light.

34. A Raman amplifier adjustment method for adjusting a Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising the steps of:

a) supplying pumping light to the fiber connecting medium;

b) measuring the received light amount;

c) detecting a received light amount throughout the entirety of a predetermined signal light band;

d) estimating, based on the pumping light amount, a noise component occurring in the fiber connecting medium;

e) controlling the pumping unit base on the received light amount detected in said step c) and the noise component estimation amount obtained in said step d);

f) obtaining a signal light amount by correcting the received light amount measured in said step b) with the use of the noise component estimating amount obtained in said step d); and

g) comparing between the signal light amount obtained in said step b) and the signal light amount obtained in said step f), and correcting the noise component estimation amount based on the comparison result.

36. The Raman amplifier adjustment method as claimed in claim 34, wherein:

a light spectrum analyzer for measuring light power at each wavelength in a wavelength band of the input light.

37. A Raman amplifier adjustment method for adjusting a Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising the steps of:

a) supplying pumping light to the fiber connecting medium;

b) estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

c) extracting a predetermined wavelength band including signal light from a received light signal, and causing a wavelength band other than said predetermined wavelength band to branch off;

d) detecting a light amount of a received light signal in the predetermined wavelength band extracted in said step c);

e) detecting a light amount of the received light signal in the wavelength band other than the predetermined wavelength band having branched off in said step c);

f) controlling said pumping unit based on the received light amounts detected in said step d) and said step e) and the noise component estimation value obtained in said step b);

g) calculating a signal light amount based on the detection result obtained in said step d);

h) calculating a signal light amount by correcting the detection result obtained in said step e) with the use of the noise component estimation value in said step b); and

i) correcting the noise component estimation value by comparing between respective calculation values obtained in said steps g) and h).

38. A Raman amplifier adjustment method for adjudging a Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising the steps of:

a) supplying pumping light to the fiber connecting medium;

b) estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

c) extracting a predetermined wavelength band including signal light from a received light signal, and causing a wavelength band other than said predetermined wavelength band to branch off;

d) detecting a light amount of a received light signal in the predetermined wavelength band extracted in said step c);

e) detecting a light amount of the received light signal in the wavelength band other than the predetermined wavelength band having branched in said step c);

f) controlling said pumping unit based on the received light amounts detected in said steps d) and e) and the noise component estimation value obtained in said step b);

g) calculating a signal light amount without correcting the detection result obtained in said step d) with the use of the noise component estimation value obtained in said step b); and

h) calculating a signal light amount by correcting the detection result in said step e) with the use of the noise component estimation value in said step b); and

i) correcting the noise component estimation value by comparing between respective calculation values obtained in said step g) and said step h).

39. A Raman amplifier adjustment method for adjusting a Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising the steps of:

a) supplying pumping light to the fiber connecting medium;

b) estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

c) causing received light signal to branch off into a first light signal and a second light signal;

d) extracting a predetermined wavelength band including a signal light through filtering said first light signal obtained in said step c);

e) detecting a light amount of a light signal extracted in said step d);

f) detecting a light amount of the second light signal obtained in said step c);

g) controlling said pumping unit based on the received light amounts detected in said steps e) and f) and the noise component estimation value obtained in said step b);

h) calculating a signal light amount based on the detection result in said step e);

i) calculating a signal light amount by correcting the detection result in said step f) with the use of the noise component estimation value obtained in said step b); and

j) correcting the noise component estimation value by comparing between respective calculation values obtained in said step h) and said step i).

40. A Raman amplifier adjustment method for adjusting a Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising the steps of:

a) supplying pumping light to the fiber connecting medium;

b) estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

c) causing received light signal to branch into a first light signal and a second light signal;

d) extracting a predetermined wavelength band including a signal light through filtering said first light signal obtained in said step c);

e) detecting a light amount of a light signal extracted in said step d);

f) detecting a light amount of the second light signal obtained in said step c);

g) controlling said pumping unit based on the received light amounts detected in said steps e) and f) and the noise component estimation value obtained in said b);

h) calculating a signal light amount without correcting the detection result in said step e) with the use of the noise component estimation value in said step b);

i) calculating a signal light amount by correcting the detection result in said step f) with the use of the noise component estimation value in said step b); and

j) correcting the noise component estimation value by comparing between respective calculation values obtained in steps h) and i).

41. A Raman amplifier adjustment method adjusting a Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising the steps of:

a) supplying pumping light to the fiber connecting medium;

b) detecting a received light amount;

c) estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

d) controlling said step a) with the use of the received light amount obtained in said step

b) and the noise component obtained in said step c);

e) causing a predetermined wavelength part without including a signal light to branch off from the received light signal;

f) monitoring a light amount of a received light signal branched off by said step e);

g) correcting the noise component estimation value by comparing between a noise component value obtained from the detection value in said step f) and the noise component estimation value obtained in said step c).

42. A Raman amplifier adjustment method for adjusting a Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising the steps of:

a) supplying pumping light to the fiber connecting medium;

b) estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

c) causing a received light signal to branch off into a first light signal and a second light signal;

d) extracting a predetermined wavelength part not including a signal light from the first light signal having branched off in said step c), by means of filtering;

e) detecting a light amount of a light signal extracted in said step d);

f) detecting a light amount of the second light signal branched off in said step c);

g) controlling said pumping unit based on the received light amounts detected in said steps e) and f) and the noise component estimation value obtained in said step b);

h) correcting the noise component estimation value by comparing between a noise component value obtained from the detection value in said e) and the noise component estimation value obtained in said step b).

43. A Raman amplifier adjustment method for adjusting a Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising the steps of:

a) supplying pumping light to the fiber connecting medium;

b) estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

c) extracting a predetermined wavelength band including a signal light and causing a wavelength band other than said predetermined wavelength band to branch off;

d) detecting a light amount of a received light signal in said predetermined wavelength band extracted in said step c);

e) detecting a light amount of a received light signal in the wavelength band other than said predetermined wavelength band having branched off in said step c);

f) controlling said step a) based on the received light amounts detected in said steps d) and e) and the noise component estimation value obtained in said step b);

g) calculating a signal light amount by correcting the detection result in said step d) with the use of the noise component estimation value obtained in said step b);

h) calculating a signal light amount by correcting the detection result in said step e) with the use of the noise component estimation value obtained in said step b); and

i) correcting the noise component estimation value by comparing between respective calculation values obtained in said step g) and said step h).

44. A Raman amplifier adjustment method for adjusting a Raman amplifier amplifying signal light with the use of a fiber connecting medium, comprising the steps of:

a) supplying pumping light to the fiber connecting medium;

b) estimating, from the pumping light amount, a noise component generated in the fiber connecting medium;

c) causing a received light signal to branch into a first light signal and a second light signal;

d) extracting a predetermined wavelength band by means of filtering from said first light signal obtained in said step c);

e) detecting a light amount of a light signal extracted in said step d);

f) detecting a light amount of said second light signal obtained in said step c);

g) controlling said step a) based on the received light amounts detected in said step e) and said step f) and the noise component estimation value obtained in said step b);

h) calculating a signal light amount by correcting the detection result in said step e) with the use of the noise component estimation value obtained in said step b);

i) calculating a signal light amount by correcting the detection result in said step f) with the use of the noise component estimation value obtained in said step b); and

j) correcting the noise component estimation value by comparing between respective calculation values in said step h) and said step i).