Mode transducer for optical wave guides

• US 3,980,392 A
• Filed: 05/01/1975
• Issued: 09/14/1976
• Est. Priority Date: 05/02/1974
• Status: Expired due to Term

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Auracher, Franz
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Levy, Stewart
• Application Number:
  US05/573,554
• Time in Patent Office: 502 Days
• Field of Search: 350/96 WG, 350/96 C
• US Class Current: 385/43
• CPC Class Codes: G02B 6/14 Mode converters
• CPC Class Codes: G02B 6/262 Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
• CPC Class Codes: G02B 6/4206 Optical features G02B6/4207, G02B6/421 take precedence
• CPC Class Codes: G02F 1/313 in an optical waveguide structure
• CPC Class Codes: H04B 10/2507 for the reduction or elimination of distortion or dispersion

Abstract

A mode transducer for use with a pair of optical wave guides for converting modes of different orders but of the same polarization to enable coupling between a first and second wave guide characterized by a coupling taper with a coupling structure arranged between the first and second wave guides with the coupling taper having an input thickness and a output thickness with the ratio of the opening angle of the mode at the input and the output of the taper being equal to the square of the ratio of the input and output thickness. In order to convert more than one mode for coupling between the first and second wave guides, the mode transducer may include a plurality of serially arranged tapers with each taper having a coupling structure and the wave guide receiving the coupled modes includes a segment of electro-optical material for each taper so that the phase of the coupled modes can be selectively changed to enable superimposition thereof.

Claims

1. A mode transducer for converting modes of different orders but of the same polarization during coupling between a pair of optical wave guides, comprising a coupling taper with a coupling structure arranged between the pair of wave guides, said coupling taper having an input thickness and an output thickness with the ratio of the opening angle of the light at the input and the output of the taper being equal to the square of the ratio of the input thickness and the output thickness;

at least one additional taper and coupling structure said additional taper and coupling structures being arranged in series with the first-mentioned taper and coupling structure so that a plurality of modes in one of the pair of wave guides are sequentially coupled into the other of said pair of wave guides; and

the other wave guide including an electrical optical segment for each of the tapers, each optical segment having separate electrodes for applying an electrical field to the electro-optical segment so that the phase speed of each mode coupled to the other wave guide can be corrected to superimpose with the other modes coupled thereto.

2. A mode transducer for converting modes of different orders but of the same polarization during coupling between a pair of optical wave guides, comprising a coupling taper with a coupling structure arranged between the pair of wave guides, said coupling taper having an input thickness and an output thickness with the ratio of the opening angle of the light at the input and the output of the taper being equal to the square of the ratio of the input thickness and the output thickness, and at least one additional taper and coupling structure, said additional taper and coupling structures being arranged in series with the first-mentioned taper and coupling structure so that a plurality of modes in one of the pair of wave guides are sequentially coupled into the other of said pair of wave guides, the coupling structure associated with each of the tapers being a directional coupler, each directional coupler being provided with an electro-optical segment having electrodes for applying an electrical field thereto so that the phase of each mode in each directional coupler can be changed for superimposing with the phase of the other modes being coupled to the other wave guide.

3. A coupling device for coupling modes of different orders but of the same polarization between a first and second optical wave guide, comprising a first optical wave guide, a second optical wave guide, and a mode transducer disposed between the first and second wave guides, said mode transducer including more than one taper arranged in series along a direction of light propagation therein and a coupling structure associated with each taper, each taper having an input end for receiving light and the associated coupling structure for coupling converted modes to the second wave guide, each taper having an input thickness and an output thickness with the ratio of the opening angle of the light at the input end to the opening angle of the light at the output end being equal to the square of the ratio of the input thickness and the output thickness, said second wave guide including a segment of electro-optical material for each taper, each segment having electrodes for applying an electrical field thereto so that the index of refraction of each segment can be changed to shift the phase of the mode coupled to the segment to enable an equal phase superimposition of the modes being converted by the tapers.

4. A coupling device for coupling modes of different orders but of the same polarization between a first and second optical wave guide, comprising a first optical wave guide, a second optical wave guide, and a mode transducer disposed between the first and second wave guides, said mode transducer including more than one taper arranged in series along a direction of light propagation therein, and a coupling structure associated with each taper, each taper having an input end for receiving light and the associated coupling structure for coupling converted modes to the second wave guide, each taper having an input thickness and an output thickness with the ratio of the opening angle of the light at the input end to the opening angle of the light at the output end being equal to the square of the ratio of the input thickness and the output thickness, the coupling structure associated with each of the tapers being a directional coupler, each directional coupler being provided with an electro-optical segment having electrodes for applying electrical field thereto so that the phase of each mode coupled into each directional coupler can be changed for superimposition with the other modes.