光纖光度系統廣泛用於監測大腦中的神經活動；然而，傳統系統通常依賴於體積龐大的光學設備，不容易由實驗動物攜帶。這種限制迫使動物在數據採集期間保持固定位置，可能影響其自然行為並降低神經信號測量的準確性。

本研究提出了一種新型光纖光度系統，結合矽光子晶片與寬動態範圍讀取電路。矽光子晶片整合了關鍵的光學元件，包括邊緣耦合器、波導、光柵耦合器和PIN光電二極體，能夠實現藍光傳輸進入腦組織以及偵測神經螢光信號。為了設計讀取電路，我們構建了一個二維光電二極體模型，用來估算光電流強度範圍，從飛米安培到奈米安培不等。在此模型的基礎上，讀取電路設計包含電流前置放大器、電流分配器和對數放大器，用於放大及處理由PIN光電二極體生成的寬動態範圍光電流信號。最終，量測結果顯示讀取電路實現了70dB的動態範圍，並將最低可檢測電流降至皮米安培。

總結來說，這套雙晶片系統成功將光纖光度技術小型化，在動物腦部植入應用方面展現了極大的潛力。此項技術進步使得能夠更精準地監測特定腦區的神經活動，為神經疾病的研究與治療策略發展提供了重要貢獻。

Fiber photometry systems are widely employed to monitor neural activity in the brain; however, conventional setups often rely on bulky optical equipment, limiting their portability for experimental animals. This constraint confines animals to fixed positions during data collection, potentially influencing their natural behavior and compromising the accuracy of neural signal measurements.

This research introduces a novel fiber photometry system that integrates silicon photonic chips with wide dynamic range readout circuits. The silicon photonic chip incorporates key optical components, including edge couplers, waveguides, grating couplers, and PIN photodiodes, to facilitate blue-light transmission into brain tissue and the subsequent detection of neuronal fluorescence signals. To inform the design of the readout circuit, a two-dimensional photodiode model was developed to estimate photocurrent intensities ranging from femtoamperes to nanoamperes. Guided by this model, the readout circuit—comprising a current pre-amplifier, current splitter, and logarithmic amplifier—was designed to amplify and process these wide-dynamic-range photocurrent signals generated by the PIN photodiodes. The measurement results indicate that the readout circuit achieves a dynamic range of 70 dB and detect currents as low as the picoampere level.

In summary, this dual-chip system effectively miniaturizes fiber photometry technology, offering significant potential for brain implantation in animals. This advancement facilitates precise monitoring of neural activity in specific brain regions, paving the way for improved understanding and treatment of neurological disorders.

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