Electrical RZ Signal Phase Control for Optical Interleaving
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In polarization multiplexed optical communication systems, the interference between TE and TM polarized optical signals leads to errors due to misalignment or improper spacing of RZ transitions, which affects system performance and requires precise control of timing to mitigate impairments such as low optical signal-to-noise ratio (OSNR) and polarization mode dispersion (PMD).
Innovation Solution
The use of phase adjusting circuits to convert NRZ electrical signals into RZ format, ensuring that RZ transitions of TE and TM polarized optical signals are either temporally aligned or spaced to optimize system performance, achieved through mixer circuits and modulators that adjust the phase of the signals to align or interleave RZ transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RZ transitions of TE and TM polarized optical signals are temporally aligned, then certain system impairments are mitigated, but other impairments worsen due to interference and interaction between polarized signals
Solution Approach 1:
The patent implements dynamic control of RZ transition timing through phase adjusting circuits that can shift the phase of electrical signals before they modulate the optical carriers. This allows the system to dynamically adjust the temporal spacing between TE and TM signal RZ transitions based on operating conditions, transforming a static timing relationship into a controllable dynamic parameter that can optimize performance while minimizing interference.
Solution Approach 2:
The invention changes the timing parameter of RZ transitions by introducing phase shifts to the electrical drive signals. By adjusting the phase of the electrical signals that drive the modulators, the system can control whether RZ transitions occur simultaneously (aligned) or at different times (spaced/interleaved), thereby optimizing system performance under different operating conditions and mitigating various types of impairments.
2Reliability
If RZ transitions of TE and TM polarized optical signals are temporally spaced or interleaved, then certain system impairments are mitigated, but other impairments worsen due to low optical signal-to-noise ratio and polarization mode dispersion
Solution Approach 1:
The system uses phase adjusting circuits to dynamically control the temporal spacing between RZ transitions of TE and TM signals. This dynamic control allows optimization of spacing to mitigate interference and polarization mode dispersion while maintaining sufficient signal power and timing synchronization to avoid worsening optical signal-to-noise ratio and other impairments.
Solution Approach 2:
By changing the phase parameter of the electrical drive signals, the system controls the temporal spacing of RZ transitions. This parameter adjustment enables optimization of the spacing to reduce polarization mode dispersion and signal interference while maintaining appropriate timing relationships to preserve optical signal-to-noise ratio and overall system performance.
3Reliability
If pulse carver is used to shape optical signals into RZ formatted pulses, then RZ format is achieved, but system cost increases and loss experienced by transmitted optical signals increases
Solution Approach 1:
The invention extracts the RZ pulse shaping function from a separate optical pulse carver component and transfers it to the electrical signal domain. By shaping the electrical drive signals into RZ format before they modulate the optical carriers, the system eliminates the need for an additional optical pulse carver, thereby reducing system cost and the cumulative loss experienced by transmitted optical signals while still achieving the desired RZ signal format.
Solution Approach 2:
The patent uses electrical RZ signals as an intermediary to achieve optical RZ formatting. Instead of directly shaping optical pulses with an optical pulse carver, the system first creates RZ-shaped electrical signals that then drive the optical modulators. This electrical intermediary approach achieves the same RZ formatting function with lower cost and reduced optical loss.
4Reliability
If additional modulator is added to modulate optical signals with data, then data modulation is achieved, but system cost increases and loss experienced by transmitted optical signals increases
Solution Approach 1:
The invention merges the data modulation function with the RZ pulse shaping function by using the same electrical RZ signals to drive the optical modulators. Instead of adding a separate pulse carver in addition to data modulators, the system combines these functions by generating RZ-shaped electrical drive signals that simultaneously provide both the timing structure for RZ format and the data modulation, thereby reducing the number of required components and associated costs.
Data Source
AI summary
Consistent with the present disclosure, polarized optical signals having the same wavelength are modulated in response to ERZ drive signals, to thereby yield corresponding RZ optical signals. Each of the polarized RZ optical signals includes a plurality of RZ transitions wherein the power of the optical signal returns to zero or a minimal power between bits or symbols. The phase or timing of the ERZ drive signals, however, is controlled, so that the RZ transitions in one polarized optical signal remain interleaved with the RZ transitions of the other polarized optical signal. Alternatively, the RZ transitions of the two polarized optical signals may be controlled so that the two are temporally aligned with one another. Thus, the timing of the RZ transitions of one polarized optical signal relative to the other polarized optical signal may be adjusted to optimize system performance.