US 2010/0303472 A1Published application

Apparatus and method for adaptively controlling the impulse response of the optical signal output from a laser of an optical transmitter (tx)

AssigneeAvago Technologies Fiber IP (Singapore) Pte. Ltd.

InventorsFrederick W. Miller, Ron Kaneshiro

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Abstract

An apparatus and a method are provided for adaptively adjusting the impulse response of the optical output of the laser of the optical TX in a way that ensures that the optical waveform being transmitted from the optical TX into the optical waveguide of the optical link has a desired waveform shape that improves or optimizes the performance of the optical link across variations in temperature, power supply, laser process corners, IC process corners, component aging, mechanical manufacturing tolerances, and part alignment tolerances. Adaptively adjusting the impulse response of the optical signal output from the laser in this way allows the optical TX to dynamically adapt to and compensate for a wide range of factors that typically cause performance degradation and result in reduced product yields, increased testing times, and increased test complexity, and higher costs. This, in turn, allows manufacturing tolerances and alignment tolerances to be relaxed, test times and test complexity to be reduced, and overall manufacturing and testing costs to be reduced.

Claims18

Dependent claims

An apparatus for use in an optical transmitter (TX) for controlling an impulse response of an optical signal produced by at least one laser of the optical TX, the apparatus comprising:

an input buffer that receives an electrical input data signal and outputs an electrical transmit (TX) signal;
a first filter circuit that receives the electrical TX signal and provides the electrical TX signal with a particular impulse response waveform, the first filter being an adaptive filter circuit having multiple taps and multiple respective tap weights that are adjustable;
a laser driver circuit that receives the electrical TX signal having the particular impulse response waveform and producing an electrical driver signal having a particular impulse response waveform;
at least one laser diode that receives the electrical driver signal and produces an optical signal in response to the electrical driver signal, the optical signal having a particular impulse response waveform;
a monitor photodiode that detects at least a portion of the optical signal produced by the laser diode and produces an electrical detection signal;
a TX high-speed (HS) amplifier that receives the electrical detection signal and produces an HS electrical output signal;
a second filter circuit that receives the HS electrical output signal and measures an impulse response of the HS electrical output signal, the second filter circuit having multiple taps and multiple respective tap weights;
an error function block configured that receives the measured impulse response and performs an error function that produces an error value corresponding to a difference between the measured impulse response and a preselected impulse response;
and
an algorithm and control logic block (ACB) that performs an adaptive impulse response algorithm that adjusts one or more of the tap weights of the first filter circuit based on the error value produced by the error function block, wherein the adjustment of one or more of the tap weights of the first filter circuit causes the impulse response of the optical signal produced by the laser diode to be adjusted.

7 more elements

A method for adjusting an impulse response of an optical signal produced by at least one laser diode of an optical transmitter (TX), the method comprising:

receiving an electrical input data signal in an input buffer of the optical TX and outputting an electrical transmit (TX) signal from the data buffer;
in a first filter circuit of the optical TX, receiving the electrical TX signal and providing the electrical TX signal with a particular impulse response waveform, the first filter being an adaptive filter circuit having multiple taps and multiple respective tap weights that are adjustable;
in a laser driver circuit of the optical TX, receiving the electrical TX signal having the particular impulse response waveform and producing an electrical driver signal having a particular impulse response waveform;
in at least one laser diode of the optical TX, receiving the electrical driver signal and producing an optical signal in response to the electrical driver signal, the optical signal having a particular impulse response waveform;
in a monitor photodiode of the optical TX, detecting at least a portion of the optical signal produced by the laser diode and producing an electrical detection signal;
in a TX high-speed (HS) amplifier of the optical TX, receiving the electrical detection signal and producing an HS electrical output signal;
in a second filter circuit of the optical TX, receiving the HS electrical output signal and measuring an impulse response of the HS electrical output signal, the second filter circuit having multiple taps and multiple respective tap weights;
in an error function block of the optical TX, receiving the measured impulse response and performing an error function to produce an error value corresponding to a difference between the measured impulse response and a preselected impulse response;
and
in an algorithm and control logic block (ACB) of the optical TX, performing an adaptive impulse response algorithm that adjusts one or more of the tap weights of the first filter circuit based on the error value produced by the error function block, wherein the adjustment of one or more of the tap weights of the first filter circuit causes the impulse response of the optical signal produced by the laser diode to be adjusted.

7 more elements

Dependencies are inferred from the claim text.