Driver for pulse amplitude modulation and optical transmitter implementing the same
First Claim
1. An optical transmitter that receives an input binary code configured with N-bits and generates an output optical signal with multiple levels, comprising:
- a semiconductor laser diode (LD);
N units of modulation sources each connected in series to the LD and in parallel to each other, the modulation sources each providing modulation currents to the LD, the modulation currents being different from each other; and
a bias source that superposes a bias current on the modulation currents,wherein the multiple levels in the output optical signal output from the LD correspond to a count and places of a HIGH level in the input binary code.
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Abstract
A pulse amplitude modulation (PAM) signal generator is disclosed. The PAM signal generator, which is applicable to a vertical cavity surface emitting laser diode (VCSEL), provides a plurality of differential units each having two outputs complementary to each other and biased by a power supply voltage through the commonly connected VCSEL and a dummy diode. The differential units have respective current sources each, where partial sums and a total sum of the currents correspond to the multiple output levels of the VCSEL. The PAM signal generator also provides compensating units to compensate the saturation (non-linearity) of the optical output of the VCSEL.
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Citations
14 Claims
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1. An optical transmitter that receives an input binary code configured with N-bits and generates an output optical signal with multiple levels, comprising:
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a semiconductor laser diode (LD); N units of modulation sources each connected in series to the LD and in parallel to each other, the modulation sources each providing modulation currents to the LD, the modulation currents being different from each other; and a bias source that superposes a bias current on the modulation currents, wherein the multiple levels in the output optical signal output from the LD correspond to a count and places of a HIGH level in the input binary code. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A driver that drives a semiconductor laser diode (LD), the driver receiving an input binary signal having N-bits, where N is greater than unity, comprising:
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a plurality of modulation sources connected in series to the LD and in parallel to each other, the modulation sources receiving respective bits in the input binary signal and providing respective modulation currents to the LD; and a bias source connected in series to the LD and in parallel to the modulation sources, the bias source superposing a bias current on the modulation currents, wherein the modulation currents each have magnitudes different from each other but have no overtone relations. - View Dependent Claims (10, 11, 12, 13, 14)
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Specification