This project presents a conceptual silicon photonic integrated circuit (PIC) floorplan for an inter-satellite optical communication transceiver.
The design focuses on radiation-tolerant system organization rather than foundry-ready implementation. It combines optical modulation, redundant primary/backup photonic paths, optical power monitoring, radiation-aware floorplanning, and receiver-side photodetection within a single integrated photonic architecture.
The main objective is to demonstrate how silicon photonics can be used to build compact and fault-aware optical communication links for space-oriented applications.
The layout was generated using a Python-based photonic design flow with gdsfactory and visualized in KLayout.
Main functional blocks include:
- input grating coupler
- 1x2 redundancy splitter
- primary and backup photonic paths
- MZI/MZM-based modulation sections
- thermal tuner sections
- optical switch sections
- monitor tap sections
- main and backup receiver photodiodes
- main and backup TIA interface blocks
- radiation monitor with ring sensor and PIN detector
- radiation isolation corridor for common-event separation
The system is organized as a simplified redundant optical transceiver architecture.
An external optical carrier is injected through the input grating coupler and split into two independent photonic paths. The primary and backup paths contain equivalent functional blocks to support redundancy at the architecture level.
flowchart LR
OPTIN[Optical Carrier Input] --> GC[Input Grating Coupler]
GC --> SPLIT[1x2 Redundancy Splitter]
SPLIT --> PMZI[Primary MZI / Modulator]
SPLIT --> BMZI[Backup MZI / Modulator]
PTX[Primary TX Driver] --> PMZI
BTX[Backup TX Driver] --> BMZI
PMZI --> PTUNER[Primary Tuner]
PTUNER --> PSW[Primary Switch]
PSW --> PTAP[Primary Monitor Tap]
PTAP --> POUT[Main Optical Output]
PTAP --> PMON[Main Monitor Output]
BMZI --> BTUNER[Backup Tuner]
BTUNER --> BSW[Backup Switch]
BSW --> BTAP[Backup Monitor Tap]
BTAP --> BOUT[Backup Optical Output]
BTAP --> BMON[Backup Monitor Output]
PMON --> PRXPD[Main RX Photodiode]
PRXPD --> PTIA[Main TIA]
BMON --> BRXPD[Backup RX Photodiode]
BRXPD --> BTIA[Backup TIA]
RADIN[Radiation Monitor Optical Access] --> RING[Ring Sensor]
RING --> PIN[PIN Detector]
The transmitter-side section uses MZI/MZM-based modulation blocks driven by symbolic TX driver interfaces. Thermal tuner sections are included to represent phase or operating-point control.
The optical signal is routed through either the primary or backup photonic path. Each path includes a switch section and a monitor tap section before reaching the corresponding output interface.
The receiver-side section contains main and backup photodiode blocks followed by TIA interface blocks. These receiver chains are represented at the system-floorplan level and are not intended as transistor-level electronic implementations.
A separate radiation monitor path includes a ring sensor and PIN detector. This block represents a local sensing structure that can be used to observe radiation-induced optical or electrical degradation effects.
The PIC layout was generated using gdsfactory and exported as a GDS layout for inspection in KLayout.
The generated design is a conceptual architecture floorplan. It shows the physical organization of the main photonic, monitoring, receiver, and radiation-aware blocks. It is not a process-qualified or foundry-ready tape-out layout.
The main layout blocks are summarized below:
| Block | Description |
|---|---|
| Input GC | Optical input interface for the external optical carrier. |
| 1x2 Redundancy Splitter | Splits the input optical signal into primary and backup paths. |
| Primary Path | Main photonic signal path with MZI, tuner, switch, and monitor tap. |
| Backup Path | Redundant photonic signal path with equivalent functional organization. |
| MZI / Modulator Section | Represents optical modulation using a Mach-Zehnder-based structure. |
| Thermal Tuner | Represents phase or operating-point tuning for the photonic path. |
| Switch Section | Represents path control or isolation functionality. |
| Monitor Tap | Extracts a portion of the optical signal for monitoring. |
| Main / Backup Output | Optical output interfaces for the primary and backup paths. |
| Main / Backup RX PD | Receiver photodiode blocks for optical-to-electrical conversion. |
| Main / Backup TIA | Receiver electronics interface blocks. |
| Radiation Monitor | Radiation-aware sensing section based on a ring sensor and PIN detector. |
| Radiation Isolation Corridor | Physical separation region used to reduce common-event sensitivity. |
| Engineering Layer Legend | Layout legend showing functional layer assignments. |
The floorplan separates the primary and backup paths spatially and places a common-event isolation region between them. This supports the radiation-tolerant architecture concept by reducing the likelihood that a single localized event affects both optical paths simultaneously.
The layout also includes named engineering layers for optical routing, photonic devices, optical I/O, primary and backup zones, RX photodiodes, thermal heaters, TX drivers, RX electronics, electrical control, radiation sensors, and the SEE isolation corridor.
Generated layout files:
gds/radiation_tolerant_inter_satellite_photonic_transceiver.gds
gds/radiation_tolerant_layers.lyp
A simplified system-level optical link budget was prepared to estimate the received optical power, photodiode current, and available link margin.
The model includes input coupling loss, MZM insertion loss, redundancy splitter loss, monitor tap loss, output coupling loss, waveguide propagation loss, and radiation-induced optical loss.
| Parameter | Value |
|---|---|
| TX optical power | 10.00 dBm |
| Input coupler loss | 2.00 dB |
| MZM insertion loss | 3.00 dB |
| Splitter loss | 3.00 dB |
| Monitor tap loss | 0.50 dB |
| Output coupler loss | 2.00 dB |
| Waveguide loss coefficient | 1.00 dB/cm |
| Waveguide length | 1.50 cm |
| Radiation-induced loss | 1.00 dB |
| Photodiode responsivity | 0.80 A/W |
| Receiver sensitivity assumption | -10.00 dBm |
| Result | Value |
|---|---|
| Waveguide loss | 1.50 dB |
| Total optical loss | 13.00 dB |
| Received optical power | -3.00 dBm |
| Received optical power | 0.5012 mW |
| Photodiode current | 0.4009 mA |
| Minimum required photodiode current | 0.0800 mA |
| Link margin | 7.00 dB |
| Link status | PASS |
| Limit | Value |
|---|---|
| Maximum allowed radiation-induced loss | 8.00 dB |
| Radiation loss margin | 7.00 dB |
| Maximum allowed waveguide length | 8.50 cm |
| Waveguide length margin | 7.00 cm |
The nominal received optical power is -3.00 dBm, which is 7.00 dB above the assumed receiver sensitivity of -10.00 dBm. Under the current assumptions, the simplified link budget passes.
The simulation also shows that the architecture can tolerate up to 8.00 dB of radiation-induced optical loss before reaching the receiver sensitivity limit. For the assumed waveguide loss of 1.00 dB/cm, the maximum allowed waveguide length is 8.50 cm.
Detailed numerical output is provided in:
simulations/results/link_budget_summary.txt
The link budget should be treated as a first-order system-level estimation. A more accurate model would require wavelength-dependent component behavior, radiation-induced loss data from measurements or literature, detector noise modeling, modulation extinction ratio, receiver bandwidth, and target bit-error-rate assumptions.
This project demonstrates a conceptual radiation-tolerant silicon photonic transceiver architecture for inter-satellite optical communication links.
The design integrates redundant primary and backup photonic paths, optical modulation, tuning, switching, monitor taps, receiver photodiode interfaces, and a radiation monitor section within a single system-level PIC floorplan.
The optical link budget confirms that, under the selected assumptions, the nominal received optical power remains above the assumed receiver sensitivity with a 7.00 dB link margin. The model also provides first-order limits for radiation-induced loss and waveguide length.
The project is not intended as a foundry-ready implementation. It should be treated as an engineering concept focused on architecture, layout organization, radiation-aware floorplanning, and first-order optical link budget analysis.