Optical modulator optical transmitter apparatus and optical transmission system

Claim 2

An optical transmitter apparatus, comprising an optical modulator (11-1) including an intensity modulator part (12-1) and a phase modulator part (13-1) optically coupled in tandem, a light source (1) for optical signal transmission, a transmit signal generator (4), an intensity modulator driver circuit (14-1), a signal generator (5) and a phase modulator driver circuit (15-1), wherein a transmit signal to be transmitted is generated by said transmit signal generator (4) and supplied to said intensity modulator driver circuit (14-1), an output of said intensity modulator driver circuit (14-1) being supplied to said intensity modulator part (12-1), and a signal generated by said signal generator (5) being supplied to said phase modulator driver circuit (15-1), whose output is supplied to said phase modulator part (13-1), and wherein a light beam emitted from said light source (1) is sent to said optical modulator (11-1) to be modulated in intensity by said intensity modulator part (12-1) while modulated in phase by said phase modulator part (13-1) to be thereby spread in spectrum, whereupon the optical signal outputted from said optical modulator (11-1) is sent out as an optical signal for transmission.

Claim 3

An optical transmitter apparatus, comprising an optical modulator (11-2) which includes a Mach-Zehnder type intensity modulator part (12-2) optically coupled in tandem to at least one phase modulator part (13-2), a light source (1) for signal transmission, a signal generator (5), an intensity modulator driver circuit (14-2), a signal generator (4) and a phase modulator driver circuit (15-2), wherein a transmit signal for transmission is generated by said transmit signal generator (4) and supplied to said intensity modulator driver circuit (14-2) whose output is supplied to said Mach-Zehnder type intensity modulator part (12-2), while a signal generated by said signal generator (5) is supplied to said phase modulator driver circuit (15-2) whose output is supplied to said phase modulator part (13-2); and wherein a light beam emitted from said light source (1) is supplied to said optical modulator (11-2) and undergoes intensity modulation in said Mach-Zehnder type intensity modulator part (12-2) and phase modulation in said phase modulator part (13-2) to be thereby spread in spectrum, the output of said optical modulator (11-2) being sent out as an optical signal for transmission.

Claim 4

An optical transmitter apparatus, comprising a light source (1) for signal transmission, a Mach-Zehnder type intensity modulator (11-3) including two phase modulator parts (12-3), a transmit signal generator (4), a signal generator (5) and an intensity modulator driver circuit (14-3) including at least two voltage combine circuits (6), wherein a transmission signal for transmission is generated by said transmit signal generator (4) and inputted to one (6-a) of said voltage combine circuits (6-a) as a signal of positive polarity while being inputted to the other one (6-b) of said voltage combine circuits (6) as a signal of negative polarity, and a signal generated by said signal generator (5) is inputted to said two voltage combine circuits (6) as a signal of same polarity, the outputs of said voltage combine circuits (6) being supplied to said two phase modulator parts (12-3a, 12-3b), respectively, of said Mach-Zehnder type intensity modulator (11-3) as outputs of said intensity modulator driver circuit (14-3), wherein a light beam emitted from said light source (1) undergoes intensity modulation and phase modulation in said Mach-Zehnder type intensity modulator (11-3) to be thereby spread in spectrum, the output signal of said Mach-Zehnder type intensity modulator (11-3) being sent out as an optical signal for transmission.

Claim 5

An optical transmitter apparatus according to claim 1, wherein said signal generator (5) generates a sinusoidal waveform signal of a frequency lower than a bit rate of said transmit signal generated by said transmit signal generator (4).

Claim 6

An optical transmitter apparatus according to claim 1, wherein said signal generator (5) generates a rectangular waveform signal of a period same as or longer than a bit duration time of said transmit signal (4) in synchronism with the latter.

Claim 7

An optical transmitter apparatus according to claim 1, wherein said signal generator (5) generates a random rectangular waveform signal in synchronism with said transmit signal (4).

Claim 8

An optical transmitter apparatus, comprising a light source (1) for signal transmission, a Mach-Zehnder type intensity modulator (11-4), a transmit signal generator (4), a digital logic circuit (16) and an intensity modulator driver circuit (14-4), wherein a transmit signal generated by said transmit generator (4) is inputted to said digital logic circuit (16), two output signals of which are inputted to said intensity modulator driver circuit (14-4), and said Mach-Zehnder type intensity modulator (11-4) modulates the light beam sent from said signal source (1) in respect to intensity and phase to thereby output an optical signal for transmission, and wherein said two signals outputted from said digital logic circuit (16) are combined such that said two output signals assume levels of "1" and "0" or levels of "0" and "1", respectively, when said transmit signal (4) is "0" while said two output signals assume "1, 1" and "0, 0" in an alternating sequence or in a random sequence when said transmit signal (4) is "1", said intensity modulator driver circuit (14-4) outputs two levels of "V-" and "V+" in correspondence to the outputs "0" and "1", respectively, of said digital logic circuit (16), and said Mach-Zehnder type intensity modulator (11-4) generates an optical signal output of substantially minimum intensity in response to the output combinations of (V+ and V-) and (V- and V+) of said intensity modulator driver circuit (14-4) while generating an optical signal output having a substantially maximum intensity and a positive optical phase in response to an output combination of (V+ and V+) of said intensity modulator driver circuit (14-4), and an optical signal output having a substantially maximum intensity and a negative optical phase is generated by said Mach-Zehnder type intensity modulator in response to an output combination of (V- and V-) of said intensity modulator driver circuit (14-4).

Claim 9

An optical transmission system, comprising an optical transmitter (100), an optical fiber (101) for optical signal transmission, and an optical receiver (103), said optical transmitter including a light source (1) for optical signal transmission, an intensity modulator (2), a transmit signal generator (4) and a signal generator (5), wherein a transmit signal for transmission is supplied from said transmit signal generator (4) to said intensity modulator (2), while a signal generated by said signal generator (5) is supplied to said phase modulator (3), and wherein a light beam emitted from said light source (1) passes through said intensity modulator (2) and said phase modulator (3) to be subsequently sent out as an optical signal for transmission with intensity thereof being modulated upon passing through said intensity modulator (2) while spectrum thereof being spread by phase modulation which said optical signal undergoes upon passing through said phase modulator (3), and wherein the optical signal outputted from said optical transmitter (100) and having intensity and phase modulated is transmitted through said optical fiber (101) to be received by said optical receiver (103).

Claim 10

An optical transmission system comprising a plurality of optical transmitters (111), an optical wavelength multiplexer (112), an optical fiber (101) for optical signal transmission, an optical wavelength demultiplexer and a plurality of optical receivers (115), said optical transmitter including a light source (1) for optical signal transmission, an intensity modulator (2), a transmit signal generator (4) and a signal generator (5), wherein a transmit signal for transmission is supplied from said transmit signal generator (4) to said intensity modulator (2), while a signal generated by said signal generator (5) is supplied to said phase modulator (3), and wherein a light beam emitted from said light source (1) passes through said intensity modulator (2) and said phase modulator (3) to be subsequently sent out as an optical signal for transmission with intensity thereof being modulated upon passing through said intensity modulator (2) while spectrum thereof being spread by phase modulation which said optical signal undergoes upon passing through said phase modulator (3), and wherein said optical signals of different wavelengths generated by said plurality of optical transmitters (111) and undergone the intensity modulation and the phase modulation are multiplexed by said optical wavelength multiplexer (112) to be subsequently outputted to said optical fiber (101) and then demultiplexed by said optical wavelength demultiplexer (114) into individual optical signals of respective wavelengths, said optical signals resulting from said demultiplexing are received by said optical receivers (115), respectively.

Claim 11

An optical transmission system comprising a plurality of optical transmitters (111), an optical coupler (116), an optical fiber (101) for optical signal transmission, an optical wavelength demultiplexer and a plurality of optical receivers (115), said optical transmitter including a light source (1) for optical signal transmission, an intensity modulator (2), a transmit signal generator (4) and a signal generator (5), wherein a transmit signal for transmission is supplied from said transmit signal generator (4) to said intensity modulator (2), while a signal generated by said signal generator (5) is supplied to said phase modulator (3), and wherein a light beam emitted from said light source (1) passes through said intensity modulator (2) and said phase modulator (3) to be subsequently sent out as an optical signal for transmission with intensity thereof being modulated upon passing through said intensity modulator (2) while spectrum thereof being spread by phase modulation which said optical signal undergoes upon passing through said phase modulator (3), and wherein said optical signals of different wavelengths generated by said plurality of optical transmitters (111) and undergone the intensity modulation and the phase modulation are multiplexed by said optical coupler (116) to be subsequently outputted to said optical fiber (101) and then demultiplexed by said optical wavelength demultiplexer (114) into individual optical signals of respective wavelengths, said optical signals resulting from said demultiplexing being received by said optical receivers (115), respectively.

Claim 12

An optical transmission system, comprising an optical transmitter apparatus (100), an optical fiber (101) for optical signal transmission and an optical receiver apparatus (103), said optical transmitter apparatus including a light source (1) for optical signal transmission, an intensity modulator (2), a phase modulator (3), a transmit signal generator (4) incorporating a clock generator circuit (21) and a data generator circuit (22), and an signal generator (5), wherein an output signal of said signal generator (5) is supplied to said phase modulator (3) and said clock generator circuit (21) incorporated in said transmit signal generator (4), the output of said clock generator circuit (21) being supplied to said data generator circuit (22) whose output is supplied to said intensity modulator (2) as the output of said transmit signal generator (4), and wherein a light beam emitted from said light source (1) passes through said intensity modulator (2) and said phase modulator (3) to be modulated in intensity upon passing through said intensity modulator (2) while modulated in phase upon passing through said phase modulator (3) to be thereby spread in spectrum, the output optical signal of said phase modulator (3) being sent out to said optical fiber (101) as an optical signal to be transmitted, which signal is received by said optical receiver (103), wherein period of the clock signal of said clock generator circuit (21) is adjusted in accordance with the output signal of said signal generator (5) so that periodical timing at which said optical signal arrives at said optical receiver (103) is substantially constant.

Claim 13

An optical transmitter apparatus, comprising a light source (1) for optical signal transmission, an intensity modulator (2), a phase modulator (3) and a transmit signal generator (4), wherein a transmit signal to be transmitted is generated by said transmit signal generator (4) and inputted to said intensity modulator (2) and said phase modulator (3), and wherein a light beam emitted from said light source (1) passes through said intensity modulator and said phase modulator (3) and undergoes intensity modulation and feeble phase modulation upon passing through said intensity modulator (2), the optical signal outputted from said intensity modulator (2) undergoing such a phase modulation upon passing through said phase modulator that a phase shift due to said feeble phase modulation by said intensity modulator can be compensated, whereby an optical signal which is not modulated in phase but modulated in intensity is sent out as an output signal of said optical transmitter apparatus.

Claim 14

An optical transmission system, comprising an optical transmitter apparatus (100-5) including a light source (1) for optical signal transmission, an intensity modulator (2-5), a phase modulator (3-5) and a transmit signal generator (4), an optical fiber (101) and an optical receiver (103), wherein a signal to be transmitted is generated by said transmit signal generator (4) and inputted to said intensity modulator (2-5) and said phase modulator (3-5), and wherein a light beam emitted from said light source (1) is sent out as an optical signal to be transmitted from said optical transmitter apparatus (100-5) after having passed through said intensity modulator (2-5) and said phase modulator (3-5), said optical signal being transmitted through said optical fiber (101) to be inputted to said optical receiver (103), wherein intensity modulation of said optical signal is effected upon passing through said intensity modulator (2-5), while upon passing through said phase modulator (3-5), the optical signal undergoes such phase modulation that deterioration of waveform of said optical signal due to dispersion encountered during transmission through said optical fiber (101) can be suppressed to a possible minimum.

Claim 15

An optical transmitter apparatus, comprising a light source (1) for optical signal transmission, an intensity modulator (2-6), a phase modulator (3-6), a transmit signal generator (4), an intensity modulator driver circuit (14-6) and a phase modulator driver circuit (15-6), wherein a transmit signal to be transmitted is generated by said transmit signal generator (4) and inputted to said intensity modulator driver circuit (14-6) and said phase modulator driver circuit (15-6), output of said intensity modulator driver circuit (14-6) being supplied to said intensity modulator (2-6) while output of said phase modulator driver circuit (15-6) being supplied to said phase modulator (3-6), and wherein a light beam emitted from said light source (1) passes through said intensity modulator (2-6) and said phase modulator (3-6) and undergoes intensity modulation and feeble phase modulation upon passing through said intensity modulator (2-6), the optical signal outputted from said intensity modulator (2-6) undergoing such a phase modulation upon passing through said phase modulator (3-6) that a phase shift due to said feeble phase modulation by said intensity modulator (2-6) can be compensated, whereby an optical signal which is not modulated in phase but modulated in intensity is sent out as an output optical signal of said optical transmitter apparatus (100-6).

Claim 16

An optical transmitter apparatus, comprising a light source (1) for optical signal transmission, an intensity modulator (2-7), a phase modulator (3-7), a transmit signal generator (4), and a modulator driver circuit (14-7), wherein a transmit signal to be transmitted is generated by said transmit signal generator (4) and inputted to said modulator driver circuit (14-7), outputs of positive and negative polarities generated by said modulator driver circuit (14-7) being supplied to said intensity modulator (2-7) and said phase modulator (3-7), respectively, and wherein a light beam emitted from said light source (1) passes through said intensity modulator (2-7) and said phase modulator (3-7) and undergoes intensity modulation and feeble phase modulation upon passing through said intensity modulator (2-7), the optical signal outputted from said intensity modulator (2-7) undergoing such a phase modulation upon passing through said phase modulator (3-7) that a phase shift due to said feeble phase modulation by said intensity modulator (2-7) can be compensated, whereby an optical signal which is not modulated in phase but modulated in intensity is sent out as an output optical signal of said optical transmitter apparatus (100-7).

Claim 17

An optical transmission system, comprising an optical transmitter apparatus (100-6) which includes a light source (1) for optical signal transmission, an intensity modulator (2-6), a phase modulator (3-6), an intensity modulator driver circuit (14-6), a phase modulator driver circuit (15-6) and a transmit signal generator (4), an optical fiber (101) and an optical receiver (103), wherein a signal to be transmitted is generated by said transmit signal generator (4) and inputted to said intensity modulator driver circuit (14-6) and said phase modulator driver circuit (15-6), output of said intensity modulator driver circuit (14-6) being supplied to said intensity modulator (2-6) while output of said phase modulator driver circuit (15-6) is supplied to said phase modulator (13-6), and wherein a light beam emitted from said light source (1) is sent out as an optical signal to be transmitted from said optical transmitter apparatus (100-6) after having passed through said intensity modulator (2-6) and said phase modulator (3-6), said optical signal being transmitted through said optical fiber (101) to be inputted to said optical receiver (103), wherein intensity modulation of said optical signal is effected upon passing through said intensity modulator (2-6), while upon passing through said phase modulator (3-6), the optical signal undergoes such phase modulation that deterioration of waveform of said optical signal due to dispersion encountered during transmission through said optical fiber (101) can be suppressed to a possible minimum.

Claim 18

An optical transmission system, comprising an optical transmitter apparatus (100-7) which includes a light source (1) for optical signal transmission, an intensity modulator (2-7), a phase modulator (3-7) and a modulator driver circuit (14-7) and a transmit signal generator (4), an optical fiber (101) and an optical receiver (103), wherein a signal to be transmitted is generated by said transmit signal generator (4) and inputted to said modulator driver circuit (14-7), outputs of positive and negative polarities generated by said modulator driver circuit (14-7) being supplied to said intensity modulator (2-7) and said phase modulator (3-7), respectively, and wherein a light beam emitted from said light source (1) is sent out as an optical signal to be transmitted from said optical transmitter apparatus (100-7) after having passed through said intensity modulator (2-7) and said phase modulator (3-7), said optical signal being transmitted through said optical fiber (101) to be inputted to said optical receiver (103), wherein intensity modulation of said optical signal is effected upon passing through said intensity modulator (2-7), while upon passing through said phase modulator (3-7), the optical signal undergoes such phase modulation that deterioration of waveform of said optical signal due to dispersion encountered during transmission through said optical fiber (101) can be suppressed to a possible minimum.

Claim 19

An optical modulator, comprising an intensity modulator part (12-6), a phase modulator part (13-6), an intensity modulator driver circuit (14-6) and a phase modulator driver circuit (15-6), wherein a modulating signal inputted to said modulator (11-6) is inputted to said intensity modulator driver circuit (14-6) and said phase modulator driver circuit (15-6), output of said intensity modulator driver circuit (14-6) being inputted to said intensity modulator part (12-6) while output of said phase modulator driver circuit (15-6) is inputted to said phase modulator part (13-6), and a light beam inputted to said optical modulator (11-6) is outputted after having passed through said intensity modulator part (12-5) and said phase modulator part (13-6), and wherein said light beam undergoes an intensity modulation and a phase modulation in said intensity modulator part (12-6), while in said phase modulator part (13-6), phase modulation is effected such that phase shift resulting from said intensity modulation by said intensity modulator part can be canceled.

Claim 20

An optical modulator, comprising an intensity modulator part (12-7), a phase modulator part (13-7) and a modulator driver circuit (14-7), wherein a modulating signal inputted to said modulator (11-7) is inputted to said intensity modulator driver circuit (14-7), outputs of positive and negative signs of said modulator driver circuit (14-7) being inputted to said intensity modulator part (12-7) and said phase modulator part (13-7), respectively, wherein a light beam inputted to said optical modulator (11-7) is outputted after having passed through said intensity modulator part (12-7) and said phase modulator part (13-7), and wherein said light beam undergoes an intensity modulation and a phase modulation in said intensity modulator part (12-7), while in said phase modulator part (13-7), phase modulation is effected such that phase shift resulting from said intensity modulation by said intensity modulator part (12-7) can be canceled.

Claim 21

An optical modulator, comprising an intensity modulator part and a phase modulator part, wherein material, structure, length and width of said intensity modulator part and/or said phase modulator part are so selected that phase modulation efficiency of said intensity modulator part substantially coincides with that of said phase modulator part.

Claim 22

An optical modulator, comprising an intensity modulator part (12-9), a phase modulator part (13-9) and a modulator driver circuit (14-9) including at least one bias circuit (7), wherein a modulating signal inputted to said modulator (11-9) is inputted to said modulator driver circuit (14-9), outputs of positive and negative signs of said modulator driver circuit (14-9) being inputted to said intensity modulator part (12-9) and said phase modulator part (13-9), respectively, while output of said bias circuit (7-a, 7-b) is inputted to said intensity modulator part or said phase modulator part, and wherein a light beam inputted to said optical modulator (11-9) is outputted after having passed through said intensity modulator part (12-9) and said phase modulator part (13-9), wherein said light beam undergoes an intensity modulation and a phase modulation in said intensity modulator part (12-9), while in said phase modulator part (13-9), phase modulation is effected such that phase shift resulting from said intensity modulation by said intensity modulator part (12-9) can be canceled.

Claim 23

An optical modulator, comprising an intensity modulator part (12-9), a phase modulator part (13-9) and a modulator driver circuit (14-9) including at least two bias circuit (7-a, 7-b), wherein a modulating signal inputted to said modulator (11-9) is inputted to said modulator driver circuit (14-9), outputs of positive and negative signs of said modulator driver circuit (14-9) being inputted to said intensity modulator part (12-9) and said phase modulator part (13-9), while being added with mutually different bias signals from said bias circuits (7-a, 7-b), respectively, and wherein a light beam inputted to said optical modulator (11-9) is outputted after having passed through said intensity modulator part (12-9) and said phase modulator part (13-9), wherein said light beam undergoes an intensity modulation and a phase modulation in said intensity modulator part (12-9), while in said phase modulator part (13-9), phase modulation is effected such that phase shift resulting from said intensity modulation by said intensity modulator part (12-9) can be canceled.

Claim 24

An optical transmitter apparatus, comprising an optical modulator, a light source (1) for optical signal transmission and a transmit signal generator (4), said optical modulator (11-6) including an intensity modulator part (12-6), a phase modulator part (13-6), an intensity modulator driver circuit (14-6) and a phase modulator driver circuit (15-6), wherein a modulating signal inputted to said optical modulator (11-6) is inputted to said intensity modulator driver circuit (14-6) and said phase modulator driver circuit (15-6), output of said intensity modulator driver circuit (14-6) being inputted to said intensity modulator part (12-6) while output of said phase modulator driver circuit (15-6) is inputted to said phase modulator part (13-6), and a light beam inputted to said optical modulator (11-6) is outputted after having passed through said intensity modulator part (12-5) and said phase modulator part (13-6), said light beam undergoing an intensity modulation and a phase modulation in said intensity modulator part (12-6), while in said phase modulator part (13-6), phase modulation is effected such that phase shift resulting from said intensity modulation by said intensity modulator part can be canceled, and wherein an output light beam of said light source and an output of said transmit signal generator are inputted to said optical modulator which modulates intensity of the light beam outputted from said light source in accordance with the output signal of said transmit signal generator without modulating the phase of the light beam outputted from said light source.

Claim 25

An optical transmitter apparatus, comprising a light source (1) for optical signal transmission, an intensity modulator (2), at least first and second phase modulators (3-a; 3-b), a transmit signal generator (4) and a signal generator (5), wherein a transmit signal to be transmitted is generated by said transmit signal generator (4) to be supplied to said intensity modulator (2) and said first phase modulator (3-a), while a signal generated by said signal generator (5) is supplied to said second phase modulator (3-b), and wherein a light beam emitted from said light source (1) passes through said intensity modulator (2) and said first and second phase modulators (3-a; 3-b) to undergo an intensity modulation and a feeble phase modulation upon passing through said intensity modulator (2) and undergo such phase modulation upon passing through said first phase modulator (3-a) that a phase shift due to said feeble modulation by said intensity modulator (2) can be compensated, while being phase-modulated upon passing through said second phase modulator (3-b) such that spectrum is spread, whereby an output optical signal of said second phase modulator is sent out as the optical signal for transmission.

Claim 26

An optical transmitter apparatus, comprising an optical modulator including an intensity modulator part and a phase modulator part optically coupled in tandem, a light source (1) for optical signal transmission, a transmit signal generator (4), an intensity modulator driver circuit, a signal generator (5) and a phase modulator driver circuit, wherein a transmit signal to be transmitted is generated by said transmit signal generator (4) and supplied to said intensity modulator driver circuit and said phase modulator driver circuit, an output of said intensity modulator driver circuit being supplied to said intensity modulator part, and a signal generated by said signal generator (5) is supplied to said phase modulator driver circuit, whose output is a signal synthesized from said transmit signal as inputted and a signal from said generator and supplied to said phase modulator part, and wherein a light beam emitted from said light source (1) is sent to said optical modulator to undergo intensity modulation and a feeble phase modulation in said intensity modulator part while undergoing such phase modulation in said phase modulator part that phase shift due to said feeble modulation is compensated while being spread in spectrum, whereupon the optical signal outputted from said optical modulator is sent out as an optical signal for transmission.

Claim 27

An optical signal transmission system, comprising a plurality of optical transmitter (111) each including a light source for optical signal transmission, an intensity modulator and a transmit signal generator, an optical wavelength multiplexer or alternatively an optical coupler (116), a signal generator (5), an optical fiber (101) for signal transmission, an optical wavelength demultiplexer (114) and a plurality of optical receivers, wherein in each of said optical transmitters (111), a transmit signal to be transmitted is generated by the associated transmit signal generator to be supplied to the associated intensity modulator for thereby modulating intensity of a light beam emitted from said light source and passing through said associated intensity modulator, whereby a transmit optical signal is outputted form each of said optical transmitters (111), and wherein the intensity-modulated transmit optical signals having different wavelengths and outputted from said plurality of optical transmitters, respectively, are multiplexed by said optical wavelength multiplexer or alternatively said coupler (116) to be subsequently inputted to said phase modulator (3) as a wavelength multiplexed signal to undergo phase modulation in accordance with an output signal of said signal generator (5), the output optical signal from said phase modulator (3) being sent out into said optical fiber (101) to be subsequently demultiplexed to individual wavelengths by said optical wavelength demultiplexer (114), wherein optical signals resulting from said demultiplexing are received by said plurality of optical receivers (115), respectively.