Optical transmitter and optical transmission method

• US 20080025732A1
• Filed: 06/06/2007
• Published: 01/31/2008
• Est. Priority Date: 07/26/2006
• Status: Active Grant

• Current Assignee: Hitachi Metals (Thailand) Ltd.
• Original Assignee: Hitachi Cable Limited (Proterial Ltd.)
• Inventors: Hattori, Keita
• Granted Patent: US 8,218,974 B2
• Time in Patent Office: Days
• US Class Current: 398/194
• CPC Class Codes: H04B 10/85 Protection from unauthorised access, e.g. eavesdrop protection

Abstract

An optical transmitter and an optical transmission method includes a plurality of light-emitting elements, a plurality of light-receiving elements for monitoring optical outputs from the light-emitting elements, a linear operation circuit for calculating optical output monitor signals by removing crosstalk parts from a plurality of photoelectric conversion currents outputted from the light-receiving elements, and a drive circuit for driving individually currents to apply to the light-emitting elements based on the optical output monitor signals.

Claims

1. An optical transmitter, comprising:

a plurality of light-emitting elements;

a plurality of light-receiving elements for monitoring optical outputs from said light-emitting elements;

a linear operation circuit for calculating optical output monitor signals by removing crosstalk parts from a plurality of photoelectric conversion currents outputted from said light-receiving elements, said crosstalk parts arising from adjacent light-emitting elements; and

a drive circuit for driving individually currents to apply to said light-emitting elements based on said optical output monitor signals.

2. An optical transmitter according to claim 1, wherein:

said linear operation circuit solves a simultaneous linear equation Σ

_jAijXj=Bi (i=1, 2, . . . , m;

j=1, 2, . . . , n), and outputs said optical output monitor signals Xj, where Aij is an optical coupling efficiency between an i-th light-receiving element of said plurality of light-receiving elements and a j-th light-emitting element of said plurality of light-emitting elements or a value in proportion to said optical coupling efficiency, Σ

j represents a summation in relation to j, and Bi is an i-th photoelectric conversion current of said plurality of photoelectric conversion currents.

3. An optical transmitter according to claim 1, wherein:

said linear operation circuit is connected to a recording and communicating unit for sending a value of said optical output monitor signals to an external device.

4. An optical transmitter according to claim 3, wherein:

said recording and communicating unit includes a memory for storing said optical output monitor signals, and a memory access interface circuit for communicating with said external device.

5. An optical transmitter according to claim 4, wherein:

said recording and communicating unit includes a comparison circuit for generating warning signals based on said optical output monitor signals and storing the warning signals in said memory.

6. An optical transmitter according to claim 2, wherein:

said linear operation circuit includes a first linear operation circuit for preprocessing with respect to said photoelectric conversion currents, and a second linear operation circuit for solving said simultaneous linear equation by substituting a result of the preprocessing by said first linear operation circuit for a right-hand member of said simultaneous linear equation.

7. An optical transmitter according to claim 1, wherein:

said light-emitting elements and said light-receiving elements are coupled optically so that an n-by-n matrix C=DA is a strictly diagonally dominant matrix |Ckk|>

Σ

<sub>j≠

k</sub>|Ckj| (k=1, 2, . . . , n;

Ckj comprises an element of the matrix C;

Σ

<sub>j≠

k</sub> comprises a symbol of a summation with respect to j=1˜

n except j=k.), which is a coefficient matrix A={Aij} constituted by Aij which comprises an optical coupling efficiency between an i-th light-receiving element of said plurality of light-receiving elements and a j-th light-emitting element of said plurality of light-emitting elements or a value in proportion to said optical coupling efficiency, multiplied by a n-by-m matrix D from a left side.

8. A method for optical transmission, comprising:

monitoring optical outputs from a plurality of light-emitting elements;

calculating optical output monitor signals by removing crosstalk parts from a plurality of photoelectric conversion currents outputted from a plurality of light-receiving elements, the crosstalk parts arising from adjacent light-emitting elements; and

driving individually currents to apply to said light-emitting elements based on said optical output monitor signals.

9. A method of optical transmission according to claim 8, further comprising:

solving a simultaneous linear equation Σ

_jAijXj=Bi (i=1, 2, . . . , m;

j=1, 2, . . . , n), and outputting said optical output monitor signals Xj,

wherein Aij is an optical coupling efficiency between an i-th light-receiving element of said plurality of light-receiving elements and a j-th light-emitting element of said plurality of light-emitting elements or a value in proportion to said optical coupling efficiency, Σ

j represents a summation in relation to j, and Bi is an i-th photoelectric conversion current of said plurality of photoelectric conversion currents.

10. A method of optical transmission according to claim 8, further comprising:

sending a value of said optical output monitor signals to an external device.

11. A method of optical transmission according to claim 10, further comprising:

storing said optical output monitor signals in a memory; and

communicating with said external device by a memory access interface circuit.

12. A method of optical transmission according to claim 11, further comprising:

generating warning signals based on said optical output monitor signals; and

storing the warning signals in said memory.

13. A method of optical transmission according to claim 9, further comprising:

preprocessing with respect to said photoelectric conversion currents; and

solving said simultaneous linear equation by substituting a result of the preprocessing for a right-hand member of said simultaneous linear equation.

14. A method of optical transmission according to claim 8, further comprising:

coupling said light-emitting elements and said light-receiving elements optically so that an n-by-n matrix C=DA is a strictly diagonally dominant matrix |Ckk|>

Σ

<sub>j≠

k</sub>|Ckj| (k=1, 2, . . . , n;

Ckj comprises an element of the matrix C;

Σ

<sub>j≠

k</sub> comprises a symbol of a summation with respect to j=1˜

n except j=k.), which is a coefficient matrix A={Aij} constituted by Aij which comprises an optical coupling efficiency between an i-th light-receiving element of said plurality of light-receiving elements and a j-th light-emitting element of said plurality of light-emitting elements or a value in proportion to said optical coupling efficiency, multiplied by a n-by-m matrix D from a left side.