Optical receiver

• US 7,903,982 B2
• Filed: 04/15/2004
• Issued: 03/08/2011
• Est. Priority Date: 04/15/2004
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Abe, Jun'ichi, Shimizu, Katsuhiro, Sugihara, Takashi
• Primary Examiner(s): Liu; Li
• Application Number:
  US10/589,349
• Publication Number:
  US 20070177885A1
• Time in Patent Office: 2,518 Days
• Field of Search: 398/26, 398/27, 398/140, 398158-164, 398202-210
• US Class Current: 398/202
• CPC Class Codes: H04B 10/66 Non-coherent receivers, e.g. using direct detection

Abstract

An optical divider divides an optical input signal into a plurality of paths. A plurality of optical-to-electrical converters respectively converts the divided optical input signals into electrical signals. A plurality of discriminators respectively outputs discrimination results by discriminating the electrical signals output from the optical-to-electrical converters based on predetermined thresholds. An operational circuit performs a predetermined logical operation with the discrimination results output from the discriminators.

Claims

1. An optical reception method comprising:

dividing, by an optical divider, an optical input signal into a plurality of paths;

converting the divided optical input signals into respective electrical signals;

outputting discrimination results by discriminating the respective converted electrical signals by utilizing a plurality of discriminators based on predetermined thresholds, wherein said predetermined thresholds imparted to the plurality of discriminators are determined according to a predetermined logical operation;

monitoring a bit error rate of an output result performed by said predetermined logical operation;

changing levels of the predetermined thresholds based on monitoring information of the bit-error-rate; and

switching a function of the logical operation based on the levels of the predetermined threshold such that

when the level of the predetermined thresholds is set to a value smaller than an optimum threshold that is used when discriminating the optical input signals divided into the paths with a single discriminator, a logical AND function is selected, and

when the level of the predetermined thresholds is set to a value larger than the optimum threshold, a logical OR function is selected.

2. The optical reception method according to claim 1, wherein

dividing the optical input signal based on a polarization state of the optical input signal.

3. The optical reception method according to claim 2, further comprising:

monitoring the respective optical signal powers on the paths; and

controlling the optical polarization based on the optical signal powers such that output values of the monitored optical signal powers become substantially equal.

4. The optical reception method according to claim 1, wherein

the predetermined thresholds of the discriminators are substantially equal.

5. An optical communication method comprising:

transmitting an optical signal; and

receiving the optical signal transmitted, wherein

the receiving includes;

dividing, by an optical divider, an optical input signal into a plurality of paths;

converting the divided optical input signals into respective electrical signals;

outputting discrimination results by discriminating the respective converted electrical signals by utilizing a plurality of discriminators based on predetermined thresholds, wherein said predetermined thresholds imparted to the plurality of discriminators are determined according to a predetermined logical operation;

monitoring a bit error rate of an output result performed b said predetermined logical operation;

changing levels of the predetermined thresholds based on monitoring information of the bit-error-rate; and

switching a function of the logical operation based on the levels of the predetermined threshold such that

when the level of the predetermined thresholds is set to a value smaller than an optimum threshold that is used when discriminating the optical input signals divided into the paths with a single discriminator, a logical AND function is selected, and

when the level of the predetermined thresholds is set to a value larger than the optimum threshold, a logical OR function is selected.

6. An optical receiver comprising:

an optical divider that divides an optical input signal into a plurality of paths;

a plurality of optical-to-electrical converters that respectively converts the divided optical input signals into electrical signals;

a plurality of discriminators that respectively outputs discrimination results by discriminating the electrical signals output from the optical-to-electrical converters based on predetermined thresholds;

an operational circuit that performs a predetermined logical operation with the discrimination results output from the discriminators;

a bit-error-rate monitoring unit that monitors a bit error rate of an output result of the operational circuit; and

a discrimination-threshold control circuit that changes levels of the predetermined thresholds of the discriminators based on monitoring information of the bit-error-rate monitoring unit, wherein

when the level of the predetermined thresholds is set to a value smaller than an optimum threshold that is used when discriminating the optical input signals divided into the paths with a single discriminator, a logical AND function is selected, and

when the level of the predetermined thresholds is set to a value larger than the optimum threshold, a logical OR function is selected.

7. The optical receiver according to claim 6, wherein

the optical divider is an optical polarization divider that divides the optical input signal based on a polarization state of the optical input signal.

8. The optical receiver according to claim 7, further comprising:

an optical polarization controller provided at a pre-stage of the optical polarization divider;

a plurality of power monitoring units that respectively monitors optical signal powers on the paths; and

a control circuit that controls the optical polarization controller based on the optical signal powers, wherein

the control circuit controls the optical polarization controller such that output values of the optical signal powers monitored by the optical monitors become substantially equal.

9. The optical receiver according to claim 6, wherein

the predetermined thresholds of the discriminators are substantially equal.

10. An optical communication system comprising:

an optical transmitter that transmits an optical signal; and

an optical receiver that receives the optical signal transmitted from the optical transmitter, wherein

the optical receiver includes

an optical divider that divides an optical input signal into a plurality of paths;

a plurality of optical-to-electrical converters that respectively converts the divided optical input signals into electrical signals;

a plurality of discriminators that respectively outputs discrimination results by discriminating the electrical signals output from the optical-to-electrical converters based on predetermined thresholds;

an operational circuit that performs a predetermined logical operation with the discrimination results output from the discriminators;

a bit-error-rate monitoring unit that monitors a bit error rate of an output result of the operational circuit; and

a discrimination-threshold control circuit that changes levels of the predetermined thresholds of the discriminators based on monitoring information of the bit-error-rate monitoring unit, wherein

the operational circuit performs a logical AND function when the level of the predetermined thresholds is set to a value smaller than an optimum threshold that is used when discriminating the optical input signals divided into the paths with a single discriminator, and

said operational circuit performs a logical OR function when the level of the predetermined thresholds is set to a value larger than the optimum threshold.

11. The optical communication system according to claim 10, wherein

the optical divider is an optical polarization divider that divides the optical input signal based on a polarization state of the optical input signal.

12. The optical communication system according to claim 11, further comprising:

an optical polarization controller provided at a pre-stage of the optical polarization divider;

a plurality of power monitoring units that respectively monitors optical signal powers on the paths; and

a control circuit that controls the optical polarization controller based on the optical signal powers, wherein

the control circuit controls the optical polarization controller such that output values of the optical signal powers monitored by the optical monitors become substantially equal.

13. The optical communication system according to claim 11, wherein

the predetermined thresholds of the discriminators are substantially equal.