Unequal spacing on multilevel signals

• US 10,720,995 B1
• Filed: 08/21/2019
• Issued: 07/21/2020
• Est. Priority Date: 08/21/2019
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Mazzini, Marco, Fludger, Christopher R. S., Cervasio, Alberto, Traverso, Matthew J.
• Primary Examiner(s): Lee, Jai M
• Application Number:
  US16/547,389
• Time in Patent Office: 335 Days
• Field of Search: None
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 10/0795 Performance monitoring; Measurement of transmission parameters
• CPC Class Codes: H04B 10/07951 Monitoring or measuring chromatic dispersion or PMD
• CPC Class Codes: H04B 10/07955 Monitoring or measuring power
• CPC Class Codes: H04B 10/0799 Monitoring line transmitter or line receiver equipment
• CPC Class Codes: H04B 10/2507 for the reduction or elimination of distortion or dispersion
• CPC Class Codes: H04B 10/2513 due to chromatic dispersion
• CPC Class Codes: H04B 10/5161 Combination of different modulation schemes
• CPC Class Codes: H04B 10/524 Pulse modulation
• CPC Class Codes: H04B 10/541 Digital intensity or amplitude modulation
• CPC Class Codes: H04J 14/0221 Power control, e.g. to keep the total optical power constant
• CPC Class Codes: H04L 25/4917 using multilevel codes

Abstract

The present disclosure provides signal management with unequal eye spacing by: sending, from a local transmitter, first and second signals with different first and second known eye patterns to a remote receiver over a channel; sending temperature data of the local transmitter and operating wavelength data of the first and second signals to the remote receiver over the channel; receiving, from the remote receiver, tuning parameters based on a dispersion of the channel based on a first difference between the first known eye pattern as transmitted and as received and a second difference between the second known eye pattern as transmitted and as received; and adjusting transmission rail values used to encode data for transmission over the channel by the local transmitter based on the tuning parameters to produce a conditioned signal for transmission with an unequally spaced eye pattern.

Claims

1. A method, comprising:

determining a dispersion slope of a channel between a transmitter and a receiver based on a temperature of the transmitter and a wavelength used by the transmitter to transmit signals over the channel;

determining a maximum power and a minimum power for transmission over the channel;

assigning a first rail to a first power level equal to the maximum power, a second rail to a second power level between the maximum power and the minimum power, a third rail to a third power level between the second power level and the minimum power, and a fourth rail to a fourth power level equal to the minimum power, wherein amplitude differences between the first, second, third, and fourth rails are based on the dispersion slope and produce a first eye pattern with a first Ratio of Level Mismatch (RLM) less than one;

encoding, by the transmitter, data onto a conditioned signal according to the first, second, third, and fourth rails; and

transmitting the conditioned signal from the transmitter to the receiver over the channel, so that the conditioned signal demonstrates a second eye pattern with a second RLM greater than the first RLM when received at the receiver.

2. The method of claim 1, wherein determining the maximum power and the minimum power further comprises:

sending, by the transmitter having a transmitter Silicon Optical Amplifier (SOA) set in bypass mode, a first optical signal over the channel to the receiver having a receiver SOA set in active mode;

sending, by the transmitter with the transmitter SOA set in active mode, a second optical signal over the channel to the receiver with the receiver SOA set in active mode;

sending, by the transmitter with the transmitter SOA set in active mode, a third optical signal over the channel to the receiver with the receiver SOA set in bypass mode; and

in response to identifying one of the first optical signal, the second optical signal, and the third optical signal as satisfying a received power requirement for the receiver, setting the transmitter SOA and the receiver SOA according to modes used in transmitting the identified one of the first optical signal, the second optical signal, and the third optical signal.

3. The method of claim 2, further comprising:

in response to determining that none of the optical first signal, the second optical signal, and the third optical signal satisfy the received power requirement, declaring a link between the transmitter and the receiver over the channel to be down.

4. The method of claim 2, further comprising:

tuning a transmitter VOA (Variable Optical Amplifier) to adjust output from the transmitter SOA to reduce back reflection from the channel onto the transmitter;

tuning a first receiver VOA in the receiver to adjust input to the receiver SOA from the channel according to a linear operating range of the receiver SOA; and

tuning a second receiver VOA to adjust output from the receiver SOA according to an operating ranges of a photodetector and a transimpedance amplifier in the receiver.

5. The method of claim 1, wherein determining the dispersion slope further comprises:

sending, from the transmitter to the receiver over the channel, a first signal with a first known eye pattern and a second signal with a second known eye pattern;

sending temperature data of the transmitter and operating wavelength data to the receiver over the channel; and

calculating the dispersion slope of the channel based a first difference between the first known eye pattern as transmitted and the first known eye pattern as received and a second difference between the second known eye pattern as transmitted and the second known eye pattern as received.

6. The method of claim 1, wherein the conditioned signal is amplified such that the second eye pattern as measured by the receiver includes:

a first received rail, that matches the maximum power;

a second received rail, that matches ⅔

of a difference between the maximum power and the minimum power;

a third received rail, that matches ⅓

of the difference between the maximum power and the minimum power; and

a fourth received rail, that matches the minimum power.

7. A method, comprising:

sending, from a local transmitter, a first signal with a first known eye pattern and a second signal with a second known eye pattern, different from the first known eye pattern, to a remote receiver over a channel;

sending temperature data of the local transmitter and operating wavelength data of the first signal and the second signal to the remote receiver over the channel;

receiving, from the remote receiver, tuning parameters based on a dispersion of the channel based on a first difference between the first known eye pattern as transmitted and as received and a second difference between the second known eye pattern as transmitted and as received; and

adjusting transmission rail values used to encode data for transmission over the channel by the local transmitter based on the tuning parameters to produce a conditioned signal for transmission with an unequally spaced eye pattern.

8. The method of claim 7, the first known eye pattern is transmitted with a first Ratio of Level Mismatch (RLM) set to one and the second known eye pattern is transmitted with a second RLM set to a predefined value less than one.

9. The method of claim 8, further comprising:

sending, from the local transmitter to the remote receiver over the channel, a third signal with a third known eye pattern set according to the tuning parameters to have a third RLM at transmission that is less than one and a fourth RLM on receipt with a value closer to one than the third RLM.

10. The method of claim 7, wherein the first signal and the second signal are pulse amplitude modulated signals with four levels.

11. The method of claim 10, wherein the tuning parameters specify:

a first transmission rail, set to a first power level equal to a maximum power for a given signal;

a second transmission rail, set to a second power level between the maximum power and a minimum power for the given signal;

a third transmission rail, set to a third power level between the second power level and the minimum power; and

a fourth transmission rail, set to a fourth power level equal to the minimum power;

wherein a first amplitude difference between the first power level and the second power level is different from a second amplitude difference between the second power level and the third power level and is different from a third amplitude difference between the third power level and the fourth power level; and

wherein the second amplitude difference is different from the third amplitude difference.

12. The method of claim 7, wherein the first signal has a first known wavelength and wherein the second signal is sent after the first signal is received by the remote receiver and has a second known wavelength different than the first known wavelength.

13. The method of claim 7, wherein wavelength division multiplexing is used over the channel, wherein the first signal and the second signal are transmitted simultaneously, wherein the first signal and the second signal are transmitted at different known wavelengths.

14. The method of claim 7, further comprising:

tuning a first amplitude of the conditioned signal as transmitted onto the channel to reduce back reflection from the channel onto the local transmitter; and

instructing the remote receiver to tune a second amplitude of the conditioned signal as received at the remote receiver to reduce nonlinearities in decoding the data encoded for transmission as received.

15. A digital signal processing device, comprising:

a processor; and

a memory storage device storing processor executable instructions that when executed by the processor, enable the processor to;

determine a dispersion of a channel between a local transmitter and a remote receiver, based on a temperature of the local transmitter and a wavelength used by the local transmitter to transmit signals over the channel;

determine a maximum power and a minimum power for transmission over the channel;

assign a first rail to a first power level equal to the maximum power, a second rail to a second power level between the maximum power and the minimum power, a third rail to a third power level between the second power level and the minimum power, and a fourth rail to a fourth power level equal to the minimum power, wherein amplitude differences between the first power level and the second power level, the second power level and the third power level, and the third power level and the fourth power level are based on the dispersion and produce a first eye pattern with a first Ratio of Level Mismatch (RLM) less than one;

encode, by the local transmitter, data onto a conditioned signal according to the first rail, the second rail, the third rail, and the fourth rail; and

transmit the conditioned signal from the local transmitter to the remote receiver over the channel, so that the conditioned signal demonstrates a second eye pattern with a second RLM greater than the first RLM when received at the receiver.

16. The digital signal processing device of claim 15, wherein to determine the maximum power and the minimum power further, the processor executable instructions, when executed by the processor, further enable the processor to:

send, by the local transmitter when a transmitter Silicon Optical Amplifier (SOA) is set in bypass mode, a first optical signal over the channel to the remote receiver when a receiver SOA is set in active mode;

send, by the local transmitter when the transmitter SOA is set in active mode, a second optical signal over the channel to the remote receiver when the receiver SOA is set in active mode;

send, by the local transmitter when the transmitter SOA is set in active mode, a third optical signal over the channel to the remote receiver when the receiver SOA is set in bypass mode; and

in response to identifying one of the first optical signal, the second optical signal, and the third optical signal as satisfying a received power requirement for the remote receiver, set the transmitter SOA to a mode used in transmitting the identified one of the first optical signal, the second optical signal, and the third optical signal.

17. The digital signal processing device of claim 16, wherein the processor executable instructions, when executed by the processor, further enable the processor to:

in response to determining that none of the first optical signal, the second optical signal, and the third optical signal satisfy the received power requirement, declare a link between the local transmitter and the remote receiver over the channel to be down.

18. The digital signal processing device of claim 16, wherein the processor executable instructions, when executed by the processor, further enable the processor to:

tune a transmitter Variable Optical Amplifier (VOA) to adjust output from the transmitter SOA to reduce back reflection from the channel onto the local transmitter.

19. The digital signal processing device of claim 15, wherein to determine the dispersion, the processor executable instructions, when executed by the processor, further enable the processor to:

send, from the local transmitter to the remote receiver over the channel, a first signal with a first known eye pattern and a second signal with a second known eye pattern;

send temperature data of the local transmitter and operating wavelength data to the remote receiver over the channel; and

receive, from the remote receiver, a calculation of the dispersion of the channel based on a first difference between the first known eye pattern as transmitted and the first known eye pattern as received and a second difference between the second known eye pattern as transmitted and the second known eye pattern as received.

20. The digital signal processing device of claim 15, wherein the conditioned signal is amplified such that the second eye pattern as measured by the remote receiver includes:

a first received rail, that matches the maximum power;

a second received rail, that matches ⅔

of a difference between the maximum power and the minimum power;

a third received rail, that matches ⅓

of the difference between the maximum power and the minimum power; and

a fourth received rail, that matches the minimum power.