Optical receiver having bias circuit for avalanche photodiode with wide dynamic range

• US 20060280511A1
• Filed: 06/08/2006
• Published: 12/14/2006
• Est. Priority Date: 06/14/2005
• Status: Active Grant

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Futami, Ryutaro
• Granted Patent: US 7,761,013 B2
• Time in Patent Office: Days
• US Class Current: 398/209
• CPC Class Codes: H04B 10/6911 Photodiode bias control, e.g. for compensating temperature variations

Abstract

An optical receiver is provided as a device capable of detecting a small optical power with satisfactory accuracy and detecting the optical power in a wide dynamic range. In the optical receiver a bias generator applies a variable voltage to an avalanche photodiode (APD). First and second current sensors generate first and second detected signals according to a photocurrent. A controller calculates an optical power, using either one of the detected signals. The first current sensor includes a current mirror circuit and generates a first detected signal by measuring an electric current proportional to the photocurrent. The second current sensor is disposed between the bias generator and the current mirror circuit, and the maximum of the photocurrent detectable by this second current sensor is greater than the maximum of the photocurrent detectable by the first current sensor.

Claims

1. An optical receiver circuit with an avalanche photodiode (APD) for receiving an optical signal and outputting a photocurrent corresponding to the optical signal, comprising:

a bias generator for supplying a bias voltage to said APD;

a first current sensor having a first detectable range and configured to detect the photocurrent;

a second current sensor having a second detectable range wider than the first detectable range and configured to detect the photocurrent; and

a controller for controlling the bias generator based on the photocurrent detected by the first or second current sensor,

the controller controlling the bias voltage to be constant based on the photocurrent detected by the first sensor upon a power of the optical signal calculated based on the photocurrent detected by the first current sensor being less than a predetermined value, and the controller decreasing the bias voltage based on the photocurrent detected by the second current sensor upon the power of the optical signal being equal to or larger than the predetermined value.

2. An optical receiver circuit according to claim 1,

wherein the first current sensor includes a current mirror circuit having a first current path connected to said APD for the photocurrent to flow on, and a second current path for an electric current proportional to the photocurrent to flow on.

3. An optical receiver circuit according to claim 1,

wherein the constant bias voltage is a bias voltage to define a multiplication factor for maximizing a reception sensitivity of the APD.

4. An optical receiver circuit according to claim 1,

wherein the controller includes a storage device for storing a look-up table for associating the power of the optical signal with the detected photocurrent and the bias voltage.

5. An optical receiver circuit with an avalanche photodiode (APD) for receiving an optical signal and outputting a photocurrent corresponding to the optical signal, comprising:

a bias generator for supplying a bias voltage to said APD;

a first current sensor having a first detectable range and configured to detect the photocurrent;

a second current sensor having a second detectable range wider than the first detectable range and configured to detect the photocurrent; and

a controller for controlling the bias generator, based on the photocurrent detected by the first or second current sensor,

the controller controlling and decreasing the bias voltage based on the electric current detected by the second sensor upon a power of the optical signal calculated based on the electric current detected by the second current sensor being larger than a predetermined value, and the controller controlling the bias voltage to be constant based on the electric current detected by the first current sensor upon the power of the optical signal being equal to or smaller than the predetermined value.

6. An optical receiver circuit according to claim 5,

wherein the first current sensor includes a current mirror circuit having a first current path connected to said APD for the photocurrent to flow on, and a second current path for an electric current proportional to the photocurrent to flow on.

7. An optical receiver circuit according to claim 5,

wherein the constant bias voltage is a bias voltage to define a multiplication factor for maximizing a reception sensitivity of the APD.

8. An optical receiver circuit according to claim 5,

wherein the controller includes a storage device for storing a look-up table for associating the power of the optical signal with the detected photocurrent and the bias voltage.

9. A method of receiving an optical signal using an avalanche photodiode (APD) to control a bias voltage to be supplied to the APD, the APD receiving the optical signal and generating a photocurrent corresponding to the optical signal, the method comprising:

(a) detecting the photocurrent by a first current sensor and by a second current sensor having a dynamic range larger than that of the first current sensor;

(b) calculating a power of the optical signal based on the photocurrent detected by the first sensor or by the second sensor, and controlling the bias voltage supplied to the APD to be constant upon the calculated power of the optical signal being equal to or smaller than a predetermined power; and

(c) decreasing the bias voltage based on a result of detection by the second current sensor upon the calculated power of the optical signal being larger than the predetermined power.

10. A method according to claim 9, wherein the power of the optical signal is calculated as a quadratic function of the detected photocurrent.