SPECTRALLY EFFICIENT MODULATION FOR AN OPTICAL-TRANSPORT SYSTEM
First Claim
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1. An apparatus, comprising:
- an optical multiplexer having first and second input ports and an output port;
a first set of one or more optical transmitters, each configured to generate a respective modulated optical signal and direct said modulated optical signal to the first input port of the optical multiplexer;
a second set of one or more optical transmitters, each configured to generate a respective modulated optical signal and direct said modulated optical signal to the second input port of the optical multiplexer, wherein;
the optical multiplexer is configured to multiplex the modulated optical signals received at the first and second input ports and direct a resulting multiplexed signal to the output port; and
at least one of said optical transmitters comprises;
a Mach-Zehnder modulator configured to generate a pulse train for the modulated optical signal generated by said optical transmitter; and
a drive circuit configured to drive said Mach-Zehnder modulator; and
a controller configured to cause said drive circuit to drive the Mach-Zehnder modulator with an electrical ac signal having a swing range that is smaller than voltage 2Vπ
, where Vπ
is a characteristic voltage of the Mach-Zehnder modulator equal to a voltage difference between a dc bias voltage for a null in a transfer function for the Mach-Zehnder modulator and a dc bias voltage for an adjacent maximum in the transfer function.
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Abstract
An optical transport system having an optical add-drop multiplexer configured to reduce inter-channel crosstalk by driving Mach-Zehnder pulse carvers in its optical transmitters with electrical drive signals whose swing range is smaller than voltage 2Vπ of said Mach-Zehnder pulse carvers.
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Citations
20 Claims
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1. An apparatus, comprising:
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an optical multiplexer having first and second input ports and an output port; a first set of one or more optical transmitters, each configured to generate a respective modulated optical signal and direct said modulated optical signal to the first input port of the optical multiplexer; a second set of one or more optical transmitters, each configured to generate a respective modulated optical signal and direct said modulated optical signal to the second input port of the optical multiplexer, wherein; the optical multiplexer is configured to multiplex the modulated optical signals received at the first and second input ports and direct a resulting multiplexed signal to the output port; and at least one of said optical transmitters comprises; a Mach-Zehnder modulator configured to generate a pulse train for the modulated optical signal generated by said optical transmitter; and a drive circuit configured to drive said Mach-Zehnder modulator; and a controller configured to cause said drive circuit to drive the Mach-Zehnder modulator with an electrical ac signal having a swing range that is smaller than voltage 2Vπ
, where Vπ
is a characteristic voltage of the Mach-Zehnder modulator equal to a voltage difference between a dc bias voltage for a null in a transfer function for the Mach-Zehnder modulator and a dc bias voltage for an adjacent maximum in the transfer function. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A WDM method, comprising:
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generating one or more first modulated optical signals using a first set of one or more optical transmitters; generating one or more second modulated optical signals using a second set of one or more optical transmitters; multiplexing the first and second modulated optical signals using an optical multiplexer having first and second input ports and an output port and configured to (i) receive the one or more first modulated optical signals at the first input port, (ii) receive the one or more second modulated optical signals at the second input port, and (iii) direct a resulting multiplexed signal to the output port; generating a pulse train for at least one of the modulated optical signals using a Mach-Zehnder modulator; and driving said Mach-Zehnder modulator with an electrical ac signal having a swing range that is smaller than voltage 2Vπ
, where Vπ
is a characteristic voltage of the Mach-Zehnder modulator equal to a voltage difference between a dc bias voltage for a null in a transfer function for the Mach-Zehnder modulator and a dc bias voltage for an adjacent maximum in the transfer function. - View Dependent Claims (17, 18, 19, 20)
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Specification