Optical Amplifier Drive Current Feedback for Signal Quality
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Solution Overview
Problem
Optical transmitters exceeding 100 Gbps per wave using multilevel amplitude modulation for long-distance transfer face challenges in maintaining signal quality due to changes in optical coupling and output power, which conventional receivers struggle to address, leading to inadequate receiving sensitivity and loss budget compliance.
Innovation Solution
An optical device with a generator, modulator, optical amplifier, current source, and controller that adjusts drive current to cancel changes in optical output power by using feedback control systems, such as SOA current feedback control, to maintain equal amplitude ratios and compensate for non-linear distortions, thereby enhancing signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an optical transmitter exceeding 100 Gbps per wave employing multilevel amplitude modulation is used for long-distance transfer, then transmission speed is improved, but signal quality deteriorates due to changes in optical coupling and output power
Solution Approach 1:
The patent implements a feedback control mechanism where the optical output power is monitored and fed back to adjust the drive current of the optical amplifier. This closed-loop system dynamically compensates for changes in optical coupling and non-linear distortions, maintaining stable signal quality even at transmission speeds exceeding 100 Gbps per wave
Solution Approach 2:
The patent adjusts the drive current parameter of the optical amplifier based on monitored optical output power levels. By dynamically changing this electrical parameter in response to optical coupling variations, the system maintains consistent optical output power and signal quality across different transmission conditions
2Reliability
If an APD or SOA is installed in the optical receiver for long-distance transfer, then receiving sensitivity is improved, but it is not possible to ensure the same receiving sensitivity for 100 Gbps multilevel modulation as for conventional NRZ optical transmitters
Solution Approach 1:
The patent applies preliminary compensation actions at the transmitter side by adjusting the drive current of the optical amplifier before signal transmission. This pre-compensation approach addresses potential signal quality issues before they affect the receiver, enabling multilevel modulation formats to achieve performance comparable to conventional NRZ systems
Solution Approach 2:
The optical amplifier with adjustable drive current acts as an intermediary device between the modulator and the optical transmission medium. By controlling this intermediate stage, the system can optimize signal characteristics for multilevel modulation formats, bridging the performance gap between different modulation types
3Loss of energy
If the SOA optically amplifies the optical signal after modulation, then loss budget requirements are met, but changes in optical coupling occur between the SOA and optical components causing signal quality deterioration
Solution Approach 1:
The patent implements real-time monitoring of optical output power from the SOA and feeds this information back to adjust the drive current. This feedback mechanism compensates for optical coupling changes between the SOA and subsequent optical components, maintaining signal quality while meeting loss budget requirements for long-distance transfer
Solution Approach 2:
The patent transforms the static SOA operation into a dynamic system where the drive current can be adjusted in real-time. This dynamic control enables the system to adapt to changing optical coupling conditions, maintaining stable signal quality despite variations in the optical path
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively cancels changes in optical output power and non-linear distortions, ensuring equal amplitude ratios and improved signal quality, even in high-rate optical transmitters, thus meeting the requirements of loss budget and maintaining signal integrity over long distances.
Implementation Method 1
The optical amplifier optically amplifies the modulated optical signal according to a drive current
Implementation Method 2
The controller acquires, from the storage, the input-output characteristics corresponding to the drive current value of the drive current supplied to the optical amplifier and controls the electric signal based on the acquired input-output characteristics
Data Source
AI summary
An optical device includes a generator, a light emitter, a modulator, an optical amplifier, a current source, a storage, and a controller. The generator generates an electric signal of a multilevel amplitude modulation method. The light emitter emits laser light. The modulator modulates the laser light using the electric signal and outputs an optical signal. The optical amplifier optically amplifies the modulated optical signal according to a drive current. The current source adjusts the drive current to be supplied to the optical amplifier. The storage previously stores an information with respect to input-output characteristics of the optical signal in the optical amplifier relative to drive current value of the drive current. The controller acquires, from the storage, the input-output characteristics corresponding to the drive current value of the drive current supplied to the optical amplifier and controls the electric signal based on the acquired input-output characteristics.