EA Modulator Linear Operation via Signal Segmentation
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Solution Overview
Problem
In optical communication networks using non-return to zero (NRZ) modulation, the high-speed optical transmitters with electro-absorption (EA) modulators face limitations when performing multi-value modulation due to non-linear modulation characteristics, leading to signal quality deterioration as the number of channels increases, limiting the number of channels that can be frequency-multiplexed in IFOF technology.
Innovation Solution
An optical transmission device with multiple EA modulators, each modulating branched lights from a single wavelength laser, and an optical power controller to adjust and multiplex the signals, allowing for linear optical modulation and accommodating multiple channels without entering the non-linear region of the EA modulator's extinction curve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple channels are frequency-multiplexed using a single optical carrier wave, then communication capacity increases and cost reduces, but the driving amplitude of the modulation signal increases causing optical modulation to enter the non-linear region of the EA modulator, deteriorating signal quality
Solution Approach 1:
The patent divides the single broadband modulation signal into multiple independent narrowband modulation signals, each modulating a separate optical carrier wave. This segmentation allows each EA modulator to operate within its linear region while collectively achieving high-capacity transmission through frequency multiplexing of the multiple optical carriers.
2Quantity of substance
If the number of channels to be frequency-multiplexed increases, then communication capacity increases, but the driving amplitude of the modulation signal increases leading to optical modulation in the non-linear region, limiting the number of channels
Solution Approach 1:
The system segments the total number of channels into multiple groups, with each group modulated by a separate EA modulator on its own optical carrier. This allows each modulator to handle a manageable number of channels within its linear operating range, while the overall system supports a much larger total number of channels through parallel operation.
Solution Approach 2:
The patent transitions from a single-dimension approach (one carrier, one modulator) to a multi-dimensional approach (multiple carriers, multiple modulators operating in parallel). This dimensional expansion allows the system to accommodate more channels by distributing the load across multiple independent modulation paths.
3Device complexity
If a single broadband link is used to accommodate multiple channels, then device complexity reduces, but the EA modulator operates in non-linear region causing signal quality deterioration
Solution Approach 1:
Instead of using a single EA modulator for broadband modulation, the patent segments the modulation function across multiple EA modulators, each handling a narrowband signal. This segmentation preserves the linear modulation characteristic of each individual modulator while achieving broadband capacity through parallel operation and frequency multiplexing.
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
Enables efficient optical modulation of multiple channels by maintaining linear operation of EA modulators, improving signal quality and increasing the number of channels that can be frequency-multiplexed, thereby enhancing the capacity and reducing costs in optical communication networks.
Implementation Method 1
electro-absorption (EA) modulators
Data Source
AI summary
An optical transmitter includes: optical modulators to optically modulate intensities of branched lights obtained by branching a laser light having a single wavelength emitted from a single light source by respective channel signals independent of each other, and output the optically modulated branched lights as optical signals; and a modulation light multiplexer to multiplex the optical signals output from the optical modulators and output a multiplexed optical signal.