Fiber-pigtailed silicon photonic sensors for methane leak detection

Field Deployment of a Portable Optical Spectrometer for Methane Fugitive Emissions Monitoring on Oil and Gas Well Pads

“…3 ). The DFB diode laser selectively targets the 2ν 3 R(4) CH 4 transition [27,28,32] at 1651 nm (6057.1 cm −1 ), specifically utilized for immunity with respect to common atmospheric constituents (e.g., H 2 O, CO 2 , CO, and other VOCs of interest). The DFB laser is housed within an integrated TEC/current-driver unit (Model CLD1015, Thorlabs, Newton, NJ, USA) and provides up to 3 mW optical throughput (accounting for all insertion losses) into the TDLAS sensor at 1651 nm ( T laser = 15 °C).…”

“…The relatively short (5 cm) path length was selected as a compromise between alignment robustness for long-term field deployments and sensitivity requirements for CH 4 leak detection, where sensors with sub-10 ppmv sensitivities yield diminishing returns for leak monitoring applications [36]. Additionally, our free-space TDLAS sensor benchmarks the performance attainable by a next-generation of integrated photonic chip sensors currently under development [18,27,31], which provide similar effective path lengths due to modal confinement limitations. These miniaturized chip sensors are intended to provide further benefits in size, weight, power, and cost (SWaP-C), and will be demonstrated in the next iteration of field testing.…”

“…Infrared (IR) absorption spectroscopy has emerged in recent years as a promising solution for trace-gas detection which requires high levels of precision and molecular specificity [16,17,18], with applications ranging from health diagnostics [19,20] to environmental [21,22] and industrial process monitoring [23]. Fundamental rovibrational transitions in the mid-IR (3–25 µm) are readily targeted using quantum (or interband) cascade laser (QCL/ICL) technologies [24,25], while weaker overtone bands are typically measurable in the near-IR (NIR) using conventional tunable diode laser absorption spectroscopy (TDLAS) [17,26,27]. In particular, CH 4 is accessible by the latter given the convenient presence of its 2ν 3 harmonic overtones in the telecommunications U-band (1625–1675 nm) [27,28], and the spectrally resolved nature of TDLAS intrinsically enables excellent species discrimination through appropriate selection of interference-free transitions.…”

“…Fundamental rovibrational transitions in the mid-IR (3–25 µm) are readily targeted using quantum (or interband) cascade laser (QCL/ICL) technologies [24,25], while weaker overtone bands are typically measurable in the near-IR (NIR) using conventional tunable diode laser absorption spectroscopy (TDLAS) [17,26,27]. In particular, CH 4 is accessible by the latter given the convenient presence of its 2ν 3 harmonic overtones in the telecommunications U-band (1625–1675 nm) [27,28], and the spectrally resolved nature of TDLAS intrinsically enables excellent species discrimination through appropriate selection of interference-free transitions. In contrast to hyperspectral imaging [29] or non-dispersive IR techniques [16], TDLAS offers both significantly improved specificity and sensitivity, with noise-equivalent absorption (NEA) < 10 −5 Hz −1/2 achievable in well-designed systems [16].…”

“…In conjunction with wind velocity sensors deployed at METEC CSU, we demonstrate successful angle-of-arrival (AOA) leak source identification, and initial work will be presented using a classical Gaussian plume model for source magnitude estimation. We envision our source estimation methods to be widely applicable to a variety of sensing configurations (optical or otherwise), while providing a comparison benchmark for a next generation integrated photonic sensors with superior size, weight, power, and cost (SWaP-C) currently under development [18,27,31].…”