Dual Ring Resonator Modulator for Low-Loss Coherent Transmission
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Solution Overview
Problem
Current optical modulation systems, particularly Mach-Zehnder modulators, face challenges such as high operation losses, nonlinear phase transitions, and unsuitability for high-order modulation formats like 4-PSK and 16QAM, limiting their effectiveness in coherent optical transmission systems.
Innovation Solution
An optical dual resonator modulation system comprising a pair of tunable ring resonators with a relative optical phase-shifter, driven by anti-correlated or correlated RF signals, to achieve a linear response and modulate input optical signals for formats like BPSK, QPSK, 8QAM, and 16QAM, using a static 180-degree phase shifter and variable optical attenuators to control phase and amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If Mach-Zehnder modulators are used for coherent optical modulation, then modulation capability is achieved, but insertion losses are high
Solution Approach 1:
The single Mach-Zehnder modulator is segmented into two separate ring resonator modulators operating in series. Each ring resonator handles a portion of the modulation function, allowing the system to achieve the required modulation capability while reducing the insertion loss of any single component through optimized resonator design and coupling.
Solution Approach 2:
The invention changes the operating parameters by using ring resonators with high quality factors (Q>1000) and operating at specific resonance conditions. This allows the system to achieve low insertion loss (below 10 dB) while maintaining modulation capability through resonant enhancement of the electro-optic effect.
2Length of stationary object
If single ring resonator modulator is used to replace Mach-Zehnder modulator, then device size is reduced, but nonlinear phase transitions occur that are unsuitable for coherent transmission
Solution Approach 1:
The phase modulation function is segmented across two ring resonators. The first ring resonator provides initial phase modulation while the second ring resonator provides additional phase control. This segmentation allows the system to maintain linear phase transitions suitable for coherent transmission while achieving compact device size through the inherent small footprint of ring resonator structures.
Solution Approach 2:
The two ring resonators are designed with asymmetric coupling conditions and different resonance frequencies relative to the optical carrier. This asymmetric design allows independent control of each resonator's contribution to the overall phase modulation, enabling linear phase transitions despite the nonlinear nature of individual resonator responses.
3Use of energy by moving object
If Mach-Zehnder modulators are used for high-order modulation formats, then modulation capability is maintained, but drive power consumption is high
Solution Approach 1:
The invention utilizes high-Q ring resonators (Q>1000) that provide strong light-matter interaction, significantly enhancing the electro-optic effect. This allows the system to achieve the required modulation depth for high-order formats (4-PSK, 16QAM) with much lower drive power compared to conventional Mach-Zeander modulators, while maintaining adaptability to various modulation formats through programmable control of the resonator parameters.
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 system achieves lower insertion losses, reduced size, and lower drive power consumption, enabling more efficient coherent modulation with improved signal-to-noise ratios, suitable for high-order modulation schemes and linear signal processing.
Implementation Method 1
The existing Mach-Zehnder type modulators are usually long (e.g., from 5 mm up to a few centimeters) because of the relatively weak electro-optic effect involved
Implementation Method 2
a relative optical phase-shifter optically coupled between said first and second optical resonators so to impart a relative optical phase shift between said bus waveguide path and said opposed waveguide path
Data Source
AI summary
Described are various embodiments of a dual optical modulator, system and method. In one embodiment, an optical modulator modulates an input optical signal having a designated optical frequency. The modulator comprises first and second tunable modulators operable around the optical frequency and operatively disposed between a bus waveguide path and an opposed waveguide path. The modulator further comprises a relative optical phase-shifter optically coupled between the tunable modulators so to impart a relative optical phase shift between the bus waveguide path and the opposed waveguide path. The tunable modulators are respectively driveable to modulate a respective resonance thereof in complimentary directions relative to the optical frequency and thereby resonantly redirect a selectable portion of the input optical signal along the opposed waveguide path such that the relative optical phase shift is imparted thereto for output. Embodiments of an optical modulation method and an IQ modulator are also described.