Leonard MacEachern

Hierarchical In-Circuit Intelligence for Optical Transceivers

Coordinating electrical, photonic, and DSP adaptation from link-level observables.

Why this work matters

Several coupled electrical, photonic, and DSP mechanisms can produce the same decline in link margin. A fast local loop may correct the symptom, but without higher-level context it can select the wrong actuator, consume unnecessary power, or disturb another loop. This work explores hierarchical in-circuit intelligence that uses link-level observables to coordinate slower supervisory decisions with fast local adaptation—seeking corrections that remain effective, power-aware, and stable as optical links become more complex.

Supervisory controller assigning transmitter and receiver adaptation parameters from link telemetry

Slower, event-driven supervisory adaptation

Δθ = π(zlink)

subject to link-margin, power-budget, and local-loop stability constraints

Link-level observables

zlink = {Q / margin, pre-FEC BER, EVM, thermal state, power}
Telemetry from the physical linkSupervisory actuator assignment
  1. Differential electrical data waveformElectrical dataDifferential voltage
  2. High-speed driver and predistorter schematicHigh-speed driver and predistorterFpre(s) and driver swing
  3. Microring optical modulatorOptical modulatorMRR or MZM
  4. Optical channel responseOptical channelChannel response |H(f)|
  5. Photodiode beside a transimpedance amplifier with feedback resistorPhotodetector and TIAPhotodiode and −ZT
  6. ADC and digital equalizerADC and equalizerADC calibration and Heq(z)
  7. Recovered eye diagram and symbol decisionsRecovered dataEye and I/Q observables

θTX

Predistortion · driver swing · modulator bias · thermal setpoint

Fast local and background adaptationContinuous correction within the transmitter and receiver

θRX

TIA operating point · ADC calibration · equalizer coefficients

When several physical mechanisms produce the same loss of link margin, what telemetry is sufficient to assign correction to the appropriate actuator?

1

Observability

Relate link-level penalties to electrical, photonic, and channel mechanisms.

2

Control allocation

Distribute correction across coupled actuators under margin and power constraints.

3

Stability and validation

Verify the hierarchy through co-simulation, hardware-in-the-loop control, and optical-link experiments.

Evaluation

Recovered link margin

Does coordinated correction restore useful operating margin?

Convergence time

How quickly does the hierarchy select and settle the correction?

Energy per bit

What power cost accompanies the recovered performance?

Unnecessary-intervention rate

How often does supervision alter a loop that did not need correction?