PAM4 signal generation apparatus

• US 10,110,402 B2
• Filed: 12/28/2017
• Issued: 10/23/2018
• Est. Priority Date: 12/29/2016
• Status: Active Grant

• Current Assignee: Hisilicon Optoelectronics Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Hisilicon Optoelectronics Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Chen, Hongmin, Cui, Zhenwei, Huang, Xi
• Primary Examiner(s): Cadeau, Wednel
• Application Number:
  US15/857,453
• Publication Number:
  US 20180191536A1
• Time in Patent Office: 299 Days
• Field of Search: 375286, 375373, 375327
• CPC Class Codes: H03K 7/02 Amplitude modulation, i.e. PAM
• CPC Class Codes: H04B 10/5053 using a parallel, i.e. shunt, combination of modulators
• CPC Class Codes: H04B 10/5161 Combination of different modulation schemes
• CPC Class Codes: H04B 10/541 Digital intensity or amplitude modulation
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0063 Single parity check
• CPC Class Codes: H04L 25/4917 using multilevel codes
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453

Abstract

A PAM4 signal generation apparatus is provided. The PAM4 signal generation apparatus includes a DFB, two EA modulators, an SOA, a PSR, a direct-current power source, two electrical-signal generators, and two amplitude-limiting amplifiers. The two electrical-signal generators and the two amplitude-limiting amplifiers are used to generate two NRZ electrical signals respectively, the DFB outputs two optical signals, the SOA amplifies an optical power of one of the optical signals, the two EA modulators use the NRZ electrical signals and the optical signals including “a large signal and a small signal” respectively to generate two NRZ optical signals respectively, and the two NRZ optical signals are multiplexed by the PSR to generate a PAM4 electrical signal. According to this apparatus, a linearity requirement is greatly lowered. PAM4 modulation is performed in an optical domain, and this prevents a PAM4 signal from being generated on an electrical signal.

Claims

1. An apparatus, comprising:

a distributed feedback laser (DFB),

a first electro-absorption (EA) modulator,

a second EA modulator,

a semiconductor optical amplifier (SOA),

a polarization beam splitting rotator (PSR),

a first electrical-signal generator,

a first amplitude-limiting amplifier,

a second electrical-signal generator,

a second amplitude-limiting amplifier,

a first direct-current power source, and

a second direct-current power source;

wherein;

an input port of the DFB is connected to the first direct-current power source, and the DFB is connected to both the first EA modulator and the SOA by using two output ports;

the first EA modulator is connected to both the first amplitude-limiting amplifier and the DFB by using two input ports, and an output port of the first EA modulator is connected to the PSR;

the SOA is connected to both the DFB and the second direct-current power source by using two input ports, and an output port of the SOA is connected to the second EA modulator;

the second EA modulator is connected to both the second amplitude-limiting amplifier and the SOA by using two input ports, and an output port of the second EA modulator is connected to the PSR;

the PSR is connected to both the first EA modulator and the second EA modulator by using two input ports;

the first electrical-signal generator is connected to the first amplitude-limiting amplifier, and the second electrical-signal generator is connected to the second amplitude-limiting amplifier;

the DFB is configured to;

receive a first direct-current bias signal input by the first direct-current power source, generate a first optical signal and a second optical signal according to the first direct-current bias signal separately, transmit the first optical signal to the first EA modulator, and transmit the second optical signal to the SOA, wherein the first optical signal and the second optical signal have a same wavelength;

the first EA modulator is configured to;

receive a first non-return-to-zero (NRZ) electrical signal input by the first electrical-signal generator by using the first amplitude-limiting amplifier, receive the first optical signal input by the DFB, obtain a first NRZ optical signal by means of modulation according to the first NRZ electrical signal and the first optical signal, and transmit the first NRZ optical signal to the PSR;

the SOA is configured to;

receive a second direct-current bias signal input by the second direct-current power source, receive the second optical signal input by the DFB, adjust an optical power of the second optical signal according to the second direct-current bias signal to obtain a second optical signal that is after optical power amplification, and transmit, to the second EA modulator, the second optical signal that is after optical power amplification;

the second EA modulator is configured to;

receive a second NRZ electrical signal input by the second electrical-signal generator by using the second amplitude-limiting amplifier, receive the second optical signal that is after optical power amplification and that is input by the SOA, obtain a second NRZ optical signal by means of modulation according to the second NRZ electrical signal and the second optical signal that is after optical power amplification, and transmit the second NRZ optical signal to the PSR; and

the PSR is configured to;

receive the first NRZ optical signal input by the first EA modulator, receive the second NRZ optical signal input by the second EA modulator, multiplex the first NRZ optical signal and the second NRZ optical signal to obtain an output signal, and output the output signal.

2. The apparatus according to claim 1, wherein the first electrical-signal generator is configured to pre-compensate the first NRZ electrical signal according to a relative delay that is between the first NRZ electrical signal and the second NRZ electrical signal and that is on a transmission optical path.

3. The apparatus according to claim 1, wherein the second electrical-signal generator is configured to pre-compensate the second NRZ electrical signal according to a relative delay that is between the second NRZ electrical signal and the first NRZ electrical signal and that is on a transmission optical path.

4. The apparatus according to claim 1, wherein a current value of the first direct-current bias signal is less than a current value of the second direct-current bias signal.

5. The apparatus according to claim 1, wherein an optical power of the first optical signal is equal to the optical power of the second optical signal.

6. The apparatus according to claim 1, wherein the SOA is configured to amplify the optical power of the second optical signal according to an optical power of the first optical signal to obtain the second optical signal that is after optical power amplification, wherein an optical power of the second optical signal that is after optical power amplification is twice the optical power of the first optical signal.

7. The apparatus according to claim 1, wherein the DFB is configured to:

adjust a reflection coefficient of a first end surface, adjust a reflection coefficient of a second end surface, generate the first optical signal by using the first end surface, and generate the second optical signal by using the second end surface.

8. The apparatus according to claim 1, wherein the first electrical-signal generator is specifically a first digital signal processor (DSP);

and

the second electrical-signal generator is a second DSP.

9. The apparatus according to claim 1, wherein the DFB is configured to:

transmit the first optical signal to the first EA modulator by using a first passive optical waveguide, and transmit the second optical signal to the SOA by using a second passive optical waveguide.

10. The apparatus according to claim 1, wherein the apparatus comprises a four-level pulse amplitude modulation (PAM4) signal generation apparatus.

11. The apparatus according to claim 6, wherein an optical power of the second NRZ optical signal generated by the second EA modulator is twice an optical power of the first NRZ optical signal generated by the first EA modulator.

12. The apparatus according to claim 10, wherein the output signal is a PAM4 signal.