Techniques for biasing lasers

1. A method for setting a bias current for lasers used in laser assemblies, the method comprising:

determining a threshold current of a plurality of laser samples that are selected from a lot of lasers;

applying a plurality of bias currents to the laser samples;

adjusting an extinction ratio to specification for each bias current;

measuring a jitter, a mask margin, and a power of each sample laser for each bias current, wherein the jitter, mask margin, and power define a preferred laser setting;

when the preferred laser setting is exceeded, determining a preferred laser bias current for each sample laser;

averaging the preferred laser bias currents to identify an average bias current; and

setting the average laser bias current as a bias current for each laser in the lot of lasers.

2. The method of claim 1 , further comprising installing each laser in a laser assembly.

3. The method of claim 2 , wherein the laser assembly is an optical receiver or transceiver.

4. The method of claim 2 , wherein the average bias current is dependent on the type of laser installed in the laser assembly.

5. The method of claim 1 , wherein applying a plurality of bias currents to the laser samples further comprises at least one of:

selecting each bias current as a fixed value above a threshold current of each of the plurality of laser samples;

selecting each bias current as a predetermined percentage above the threshold current of each laser sample; and

selecting each bias current as a combination of the threshold current and a slope efficiency of each laser sample.

6. A method for setting a bias current for a group of optical transceivers, the optical transceivers each having a laser selected from a group of lasers the method comprising:

for each sample laser selected from a group of lasers:

determining a threshold current of each sample laser;

determining a slope efficiency of each sample laser;

determining a roll-off bias current for the sample laser to cause the sample laser output power to fall within a roll-off region; and

determining a preferred bias current for each sample laser based on the threshold current, the slope efficiency and the roll-off bias current; and

averaging the bias current from each of the sample lasers to determine an average bias current; and

setting the average bias current as a bias current for each optical transceiver that includes a laser from the group of lasers.

7. The method of claim 6 , further comprising applying additional bias currents to each sample laser to determine the preferred bias current.

8. The method of claim 7 , wherein determining a preferred bias current for each sample laser based on the threshold current further comprises:

adjusting an extinction ratio to meet a specification of each sample laser; and

measuring a current setting until the current setting is exceeded by a particular bias current, the current setting including a measurement of a jitter, a mask margin, and a power of each sample laser.

9. A computer program product for use in a computer system, the computer program product comprising a computer-readable medium storing computer-executable instructions for implementing a method for setting a bias current for a plurality of lasers, the method comprising:

determining a threshold current of a plurality of laser samples;

applying a plurality of bias currents to the laser samples;

adjusting an extinction ratio to specification for each bias current;

measuring a jitter, a mask margin, and a power of each sample laser for each bias current, wherein the jitter, mask margin, and power define a preferred laser setting;

when the preferred laser setting is exceeded, determining a preferred laser bias current for each sample laser;

averaging the preferred laser bias currents to identify an average bias current; and

setting the average laser bias current as a bias current for each laser in the lot of lasers.

10. A computer program product for use in a computer system, the computer program product comprising a computer-readable medium storing computer-executable instructions for implementing a method for setting a bias current for a group of optical transceivers, the optical transceivers each having a laser selected from a group of lasers, the method comprising:

for each sample laser selected from a group of lasers:

determining a threshold current of each sample laser;

determining a slope efficiency of each sample laser;

determining a roll-off bias current for the sample laser to cause the sample laser output power to fall within a roll-off region; and

determining a preferred bias current for each sample laser based on the threshold current, the slope efficiency and the roll-off bias current; and

averaging the bias current from each of the sample lasers to determine an average bias current; and

setting the average bias current as a bias current for each optical transceiver that includes a laser from the group of lasers.

11. In a system that includes a group of transceivers having lasers, the lasers having different threshold currents, a method for setting a bias current for each transceiver such that substantially each transceiver in the group of transceivers achieves a power within a specification of each transceiver and a ΔI that is large enough for adequate laser speed and within a roll-off region, the method comprising:

determining a threshold current for one or more sample transceivers selected from a group of transceivers, each transceiver having a laser from a particular group of lasers;

applying a plurality of bias currents to each sample;

determining a preferred bias current for each sample transceiver based on at least one factor, wherein the preferred bias current results in an output power that is within a desired output range and provides a ΔI that enables each sample transceiver to provide output at an adequate speed and without operating in a roll-over region;

determining an average bias current by averaging the preferred bias currents of the sample transceivers; and

setting the average bias current as the bias current for each transceiver in the group of transceivers.

12. A method as defined in claim 11 , wherein applying a plurality of bias currents to each sample further comprises at least one of:

selecting each bias current as being a fixed amount over the threshold current;

selecting each bias current as being a predetermined percentage above the threshold current; and

selecting each bias current as being a combination of the threshold current and a slope efficiency.

13. A method as defined in claim 11 , wherein determining a preferred bias current for each sample transceiver based on at least one factor further comprises determining the preferred bias current based on a current setting, wherein the current setting is related to a jitter, a mask margin, and an output power.

14. A method as defined in claim 11 , wherein determining the preferred bias current based on a current setting further comprises:

determining when a jitter exceeds a predetermined limit;

determining when a mask margin decreases below an predetermined value; and

determining when the output power moves outside a particular power band.

15. A method for determining a bias current for a laser, the method comprising:

determining a threshold current of a laser;

applying a plurality of bias currents to the laser, each bias current being related to the threshold current;

adjusting an extinction ratio of the laser to a specification for each bias current;

measuring a mask margin for each bias current applied to the laser; and

determining a preferred bias current for the laser, the determination being based at least in part upon the measured mask margins.

16. The method as recited in claim 15 , wherein each of the plurality of bias currents are one of:

a different fixed value above the threshold current;

a different predetermined percentage above the threshold current; and

a different combination of the threshold current and a slope efficiency of the laser.

17. The method of claim 15 , wherein a relationship between the preferred bias current and the mask margins is such that a mask margin lower than a predetermined value is indicative that the preferred bias current has been exceeded.