Optical characteristic measuring apparatus, the method thereof and recording medium

• US 6,678,041 B2
• Filed: 06/01/2001
• Issued: 01/13/2004
• Est. Priority Date: 07/10/2000
• Status: Expired due to Fees

• Current Assignee: Advantest Corporation
• Original Assignee: Advantest Corporation
• Inventors: Inui, Fumio, Imamura, Motoki, Kimura, Eiji
• Primary Examiner(s): Nguyen, Tu T.
• Application Number:
  US09/870,723
• Publication Number:
  US 20020003621A1
• Time in Patent Office: 956 Days
• Field of Search: 356/73.1, 356/218, 356/239.2, 356/434, 356/226, 359/154, 359/173, 359/181, 375/147, 375/346, 375/143, 375/353, 375/333, 375/232, 375/240, 360/65, 360/46, 360/68, 360/31, 360/25
• US Class Current: 356/73.1
• CPC Class Codes: G01M 11/333 using modulated input signals
• CPC Class Codes: G01M 11/335 using two or more input wavelengths
• CPC Class Codes: G01M 11/338 by measuring dispersion other than PMD, e.g. chromatic dispersion

Abstract

An apparatus capable of reducing a waveform distortion of outgoing light when light of an optical wavelength in a certain specific narrow range is incident upon optical fiber comprises optical source 10 for supplying the incident light to optical fiber line 110, waveform monitor 42 for measuring a waveform distortion of the transmitted light and adjusting unit 44 for adjusting an output of the incident light so that the measured waveform distortion falls within a predetermined range. By adjusting the output of the incident light, a S/N ration is lowered. Since the noise exists within a relatively wide range of wavelength, the rang of wavelength of the incident light is widened. Therefore, it is possible to reduce the waveform distortion of the outgoing light.

Claims

1. An optical characteristic measuring apparatus for measuring a characteristic of a light transmitting objective, said apparatus comprising:

an incident light supplying element for supplying incident light to said objective;

a waveform distortion measuring element for measuring a waveform distortion degree of the light transmitted from said objective; and

an optical output adjusting element for adjusting an output of the incident light prior to supplying the incident light to the objective so that

(i) the output of the incident light, after being adjusted by the optical output adjusting element, has a range of wavelengths wider than that of the input of the incident light which has not been adjusted by the optical output adjusting element yet, and wider than that of the output of the incident light if assuming that the incident light is directly supplied to the objective without being adjusted by the optical output adjusting element, and

(ii) said waveform distortion degree measured by said waveform distortion measuring element falls within a predetermined range.

2. An optical characteristic measuring apparatus according to claim 1, wherein said predetermined range is a range in which said measured waveform distortion degree is minimum.

3. An optical characteristic measuring apparatus according to claim 1, wherein said incident light supplying element comprises:

a variable wavelength light source for generating variable wavelength light;

a power supply of a modulating frequency, which is used to modulate the variable wavelength light; and

an optical modulator for modulating said variable wavelength light into said modulating frequency;

said apparatus further comprising;

a photoelectric converting element for photoelectrically converting said transmitted light;

a phase comparing element for measuring a phase difference between an output of said photoelectric converting element and an output of said power supply; and

a characteristic calculating element for determining a group delay or a wavelength dispersion of said objective from said phase difference.

4. The apparatus of claim 1, wherein said optical output adjusting element lowers a signal-to-noise ratio of the incident light.

5. The apparatus of claim 4, wherein said optical output adjusting element lowers a power level of the incident light.

6. An optical characteristic measuring method for measuring a characteristic of a light transmitting objective, said method comprising the steps of:

supplying incident light to said objective;

measuring a waveform distortion degree of the light transmitted from said objective; and

adjusting an output of the incident light so that (i) a range of wavelengths of the incident light becomes wider , and (ii) said waveform distortion degree measured in said measuring step falls within a predetermined range.

7. The method of claim 6, wherein said adjusting step comprises lowering a power level of the incident light.

8. A computer-readable medium having a program of instructions for execution by a computer to perform an optical characteristic measuring process for measuring a characteristic of a light transmitting objective, said optical characteristic measuring process comprising:

supplying incident light to said objective;

measuring a waveform distortion degree of the light transmitted from said objective; and

adjusting an output of the incident light so that (i) a range of wavelengths of the incident light becomes wider , and (ii) said waveform distortion degree measured in said measuring step falls within a predetermined range.

9. The computer-readable medium of claim 8, wherein said adjusting processing comprises lowering a power level of the incident light.