Optical loopback apparatus

• US 6,122,420 A
• Filed: 03/30/1998
• Issued: 09/19/2000
• Est. Priority Date: 03/31/1997
• Status: Expired due to Fees

• Current Assignee: Yokogawa Electric Corporation
• Original Assignee: Ando Electric Co., Ltd. (Yokogawa Electric Corporation)
• Inventors: Satoh, Yoshinori
• Primary Examiner(s): NGO, HUNG NHAT
• Application Number:
  US09/050,456
• Time in Patent Office: 904 Days
• Field of Search: 385/33, 385/34, 385/35, 385/18, 385/23, 385/47, 385/45, 385/51, 385/79
• US Class Current: 385/33
• CPC Class Codes: G02B 6/266 the optical element being an attenuator
• CPC Class Codes: G02B 6/2817 using reflective elements to split or combine optical signals
• CPC Class Codes: G02B 6/2937 In line lens-filtering-lens devices, i.e. elements arranged along a line and mountable in a cylindrical package for compactness, e.g. 3- port device with GRIN lenses sandwiching a single filter operating at normal incidence in a tubular package
• CPC Class Codes: G02B 6/2938 for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM
• CPC Class Codes: G02B 6/32 having lens focusing means positioned between opposed fibre ends with lens being an integral part of the single fibre end G02B6/262
• CPC Class Codes: G02B 6/3827 Wrap-back connectors, i.e. containing a fibre having an U shape
• CPC Class Codes: G02B 6/3845 ferrules comprising functional elements, e.g. filters

Abstract

An optical loopback apparatus provides a basis for miniaturizing the loop back mechanism so as to enable optical attenuation and wavelength multi/demultiplexing operations to be carried out in a compact device. An optical fiber unit has two single core fibers for input and output fiber paths. By aligning the central axis between the cores with the optical axis of a lens having a refractive index distribution of 0.25 pitch, the input beam into the apparatus is wholly reflected back 180 degrees by a total reflection film provided at the output terminal surface of the lens. In another arrangement, the optical axis of all four components: the central axis of the input and output fiber paths; the first lens; a second lens and a second optical fiber; are aligned, then, an input beam into the first lens is partially looped back 180 degrees at the reflective film.

Claims

1. An optical loopback apparatus comprising:

a first optical fiber having an input fiber path and an output fiber path formed into an integral parallel unit; and

a first lens having a one terminal surface coupled optically to one end section of said first optical fiber and having a reflective film formed on an other terminal surface opposing said one terminal surface,

wherein said first lens is provided with a refractive index distribution having a 0.25 pitch, and wherein a central axis between said input fiber path and said output fiber path is aligned with an optical axis of said first lens.

2. An apparatus according to claim 1, wherein said reflective film comprises a total reflection film which reflects a beam injected into said input fiber path back to said output fiber path without loss of optical energy.

3. An apparatus according to claim 1, wherein said reflective film comprises a film having a selected optical attenuation factor and reflects back a beam injected into said input fiber path at a specific reflection factor to said output fiber path.

4. An apparatus according to claim 1, wherein said reflective film comprises a specific wavelength-selective film and reflects back, in whole, such light having not less than one specific wavelength or such light having not less than a specific range of wavelengths to be output from said output fiber path.

5. An optical loopback apparatus comprising:

a first optical fiber having an input fiber path and an output fiber path formed into an integral parallel unit;

a first lens having a one terminal surface coupled optically to one end section of said first optical fiber and having a reflective film formed on an other terminal surface opposing said one terminal surface;

a second lens having a one terminal surface opposing said reflective film formed on said first lens; and

a second optical fiber having an input surface opposing an other terminal surface of said second lens;

wherein

a central axis between said input fiber path and said output fiber path, an optical axis of said first lens, an optical axis of said second lens and an optical axis of said second optical fiber are aligned.

6. An apparatus according to claim 5, wherein said first lens is provided with a refractive index distribution having a 0.25 pitch.

7. An apparatus according to claim 5, wherein said reflective film is comprised by a reflective film which reflects back a beam of light injected into said input fiber path at a specific reflection factor and transmits remaining portion of light at a selected optical transmission factor to be output to said second optical fiber, thereby distributing said input beam of light in a specific distribution ratio.

8. An apparatus according to claim 6, wherein said reflective film is comprised by a reflective-film which reflects back a beam of light injected into said input fiber path at a specific reflection factor and transmits remaining portion of light at a selected optical transmission factor to be output to said second optical fiber, thereby distributing said input beam of light in a specific distribution ratio.

9. An apparatus according to claim 5, wherein said reflective film is comprised by a wavelength-selective film reflecting back, in whole, such light having not less than one wavelength or a specific range of wavelengths, to said output fiber path, while transmitting such light having not less than one wavelength or not less than a specific range of wavelengths, exclusive of a reflected wavelength, through said output fiber path, thereby providing a wavelength multi/demultiplexing capability.

10. An apparatus according to claim 6, wherein said reflective film is comprised by a wavelength-selective film reflecting back, in whole, such light having not less than one wavelength or a specific range of wavelengths, to said output fiber path, while transmitting such light having not less than one wavelength or not less than a specific range of wavelengths, exclusive of a reflected wavelength, through said output fiber path, thereby providing a wavelength multi/demultiplexing capability.