HIGH DYNAMIC RANGE APD OPTICAL RECEIVER FOR ANALOG APPLICATIONS

• US 20110158656A1
• Filed: 12/31/2009
• Published: 06/30/2011
• Est. Priority Date: 12/31/2009
• Status: Active Grant

• Current Assignee: ARRIS Enterprises LLC (CommScope Holding Company, Inc.)
• Original Assignee: General Instrument Corporation (CommScope Holding Company, Inc.)
• Inventors: Vieira, Amarildo C., Khalouf, Ihab E.
• Granted Patent: US 8,195,055 B2
• Time in Patent Office: Days
• US Class Current: 398/202
• CPC Class Codes: H04B 10/6911 Photodiode bias control, e.g. for compensating temperature variations

Abstract

An optical receiver includes a light receiving element such as an avalanche photodiode (APD) for converting an optical signal to an electrical photocurrent amplified by a first current gain value and a temperature sensor for measuring the temperature of the light receiving element. The optical receiver also includes a control unit configured to control a bias voltage applied to the light receiving element such that the first gain value is adjusted to a second gain value based at least in part on a predetermined relationship between the current gain, the temperature and the applied bias voltage. The second current gain value is based at least in part on one or more parameters characteristic of the optical receiver and a system in which the optical receiver is employed.

Claims

1. An optical receiver, comprising:

a light receiving element for converting an optical signal to an electrical photocurrent amplified by a first current gain value;

a temperature sensor for measuring temperature of the light receiving element;

a control unit configured to control a bias voltage applied to the light receiving element such that the first gain value is adjusted to a second gain value based at least in part on a predetermined relationship between the current gain, the temperature and the applied bias voltage, wherein the second current gain value is based at least in part on one or more parameters characteristic of the optical receiver and a system in which the optical receiver is employed.

2. The optical receiver of claim 1 further comprising a memory storing a transfer function relating values of the bias voltage and the temperature to current gain values generated by the light receiving element.

3. The optical receiver of claim 1 wherein the second current gain value is further based at least in part on a first value of the photocurrent when amplified by the first gain value.

4. The optical receiver of claim 1 wherein the control unit is further configured to determine the first value of the photocurrent from the first gain value and an input current applied to the light receiving element when the photocurrent is amplified by the first gain value.

5. The optical receiver of claim 1 wherein the light receiving element is an avalanche photodiode (APD) and the second current gain value is an optical current gain that maximizes a dynamic range of the APD.

6. A method of converting an optical signal to an electrical signal, comprising:

detecting an optical signal with a light receiving element;

converting the optical signal to an electrical signal;

determining a first bias voltage value and a first input current value applied to the light receiving element;

obtaining a first value of the photocurrent generated by the light receiving element;

selecting a desired second value of the current gain based at least in part on the first value of the photocurrent and one or more parameters characteristic of the optical receiver and a system in which the optical receiver is employed;

obtaining a second value of the bias voltage that causes the light receiving element to impart the second value of the current gain to the optical signal; and

applying the second value of the bias voltage to the light receiving element.

7. The method of claim 6 wherein obtaining the first value of the photocurrent generated by the light receiving element comprises:

determining a temperature of the light receiving element;

determining a first value of the current gain from a predetermined relationship between the current gain, the temperature and the applied bias voltage;

determining the first value of the photocurrent generated by the light receiving element from the first value of the current gain and the first value of the input current.

8. The method of claim 6 wherein the desired second value of the current gain is an optimal current gain that maximizes a dynamic range of the light receiving element.

9. The method of claim 8 wherein the optimal current gain is determined based at least in part on a noise power ratio of the optical receiver and the system in which the optical receiver is employed.

10. The method of claim 6 wherein the one or more parameters characteristic of the optical receiver and the system in which the optical receiver is employed includes composite intermodulation noise arising from a transmitter and receiver in the system, a signal power received by the optical receiver from the transmitter, and a bandwidth of a channel over which is signal is transmitted.

11. The method of claim 8 wherein the light receiving element is an avalanche photodiode (APD).

12. The method of claim 6 wherein the light receiving element is an avalanche photodiode (APD) and the one or more parameters characteristic of the optical receiver and the system further includes APD excess noise.

13. The method of claim 6 wherein the desired second value of the current gain is an optimal current gain based at least in part on a figure of merit.

14. The method of claim 13 wherein the figure of merit is a modulation error rate.

15. The method of claim 11 wherein the first and second bias voltages are below a breakdown voltage of the APD.

16. An optical communication network, comprising:

an optical transmitter unit for generating optical signals;

at least one node for providing the optical signals to a plurality of optical network units;

a first link optically coupling the optical transmitter unit to the optical node, wherein the optical node includes an optical receiver for receiving optical signals from the optical network units, the optical receiver including;

a light receiving element for receiving the optical signals; and

a control unit configured to control a bias voltage applied to the light receiving element such that the light receiving element imparts a prescribed current gain to the optical signal based at least in part on one or more parameters characteristic of the optical receiver and the optical communication network.

17. The optical communication network of claim 16 wherein the one or more parameters characteristic of the optical receiver and the optical communication network in which the optical receiver is employed includes composite intermodulation noise arising from a transmitter and receiver in the system, a signal power received by the optical receiver from the transmitter, and a bandwidth of a channel over which is signal is transmitted.

18. The optical communication network of claim 16 wherein the light receiving element is an avalanche photodiode (APD) and the one or more parameters characteristic of the optical receiver and the optical communication network further includes APD excess noise.

19. The optical communication network of claim 16 wherein, for the prescribed current gain, the control unit is configured to determine the bias voltage based at least in part on a predetermined relationship between current gain, a temperature of the light receiving element, and applied bias voltage.

20. The optical communication network of claim 19 wherein the optical receiver further comprises a memory storing a transfer function relating values of the bias voltage and temperature to current gain values generated by the light receiving element.

21. The optical communication network of claim 16 wherein the light receiving element is an avalanche photodiode (APD) and the second current gain value is an optical current gain that maximizes a dynamic range of the APD.