A fast spectrometer based FBG interrogator will be discussed. This unit is constructed around a fast linear InGaAs array
with 1024 pixels and capable of reading out 40000 lines per second. This array is integrated in a double reflective
grating spectrometer, dispersing the spectra in the [1510 - 1590 nm] band. The signal treatment electronics is capable of
determining the peak wavelength position of at least 8 birefringent FBG sensors or 16 single FBG sensors at the data
rate, supplied by the image sensor.
We report on the design and development of the large linear SWIR focal plane arrays to be deployed in the multispectral
instrument of the Proba-V satellite. These sensors are based on mechanical butting of three InGaAs photodiode arrays
with 1024 pixels on 25 μm pitch, forming a nearly continuous line of 3072 pixels. A new read-out integrated circuit
(ROIC) for photocurrent integration and signal multiplexing with 1024 inputs was designed and manufactured by
stitching due to the length of the chip. The ROIC (XRO3508) includes both correlated double sampling (CDS) and autozero
features, enabling a very low Dark Signal Non Uniformity (DSNU) and Photoresponse Non-Uniformity (PRNU)
less than 0.5% of the available signal range.
Proc. SPIE. 7826, Sensors, Systems, and Next-Generation Satellites XIV
KEYWORDS: Staring arrays, Readout integrated circuits, Signal to noise ratio, Short wave infrared radiation, Indium gallium arsenide, Capacitors, Sensors, Personal digital assistants, Capacitance, Cadmium sulfide
Proba-V is a Belgian mini-satellite, designed to bridge the gap between the present Spot-Vegetation Mission and the
future GMES Sentinel missions. In order to continue the information gathering the earth surface shall be scanned in 3
Vis/NIR bands and 1 SWIR band. In this paper we will mainly focus on the development of the SWIR band FPA,
whereas other contributors will discuss more in detail the mission and the overall optical concept.
The SWIR FPA is a long linear array of 68 mm, as long as the visual detector array; due to the fact that the SWIR FPA is
a hybrid one with a detector array and a silicon readout circuit, the resolution of the SWIR array is halved wrt the visible
array. InGaAs, grown lattice matched on an InP substrate and operated at room temperature, is selected as the baseline
Due to the length of the linear array w.r.t. the InGaAs wafer size; it was decided to compose the overall FPA of several
subparts. During the architecture study, it was decided to aim for a mechanically butted array with 3 staggered sensors
lines, which are separated by 1.5 mm. App 140 pixels are foreseen in the overlap in order to realign the ground
The pixel alignment over the full array can be maintained within the following error margins: in plane (X- and Yorientation)
: ≤ 25 μm and out of plane (Z-direction): &≤ 100 μm.
The detectors are wire bonded to the Silicon readout circuit. The detector interface is a CTIA with selectable gain or
sensitivity. The nominal Feedback capacitor is 600 fF, resulting in a sensitivity of 270 nV/e-. The analog signal path is
further equipped with a CDS stage and a S&H bank.
The power dissipation of the array in slow scan mode is below 300 mW per module or < 900 mW for the FPA. The
noise of the array is measured to be below 1 mVrms on a signal swing of 2 Vptp , resulting in a circuit dynamic range of
In this paper, we outline the functionality of a new Fiber Bragg Grating (FBG) interrogator that has been developed
based on requirements from the Flight Test Group of a major European aircraft manufacturer and give some
performance figures regarding the dynamic measurement capabilities of the system. The interrogator is designed for
sensing the wavelength of short apodized gratings at high sampling rates and with strict requirements on the signal
quality in the frequency domain. In particular, the specifications on aliasing and phase distortion will be discussed, and
an explanation on how the system can and does meet these specs over different sampling frequencies is given.
InGaAs is the material of preference for uncooled imaging in the [0.9-1.7 μm] SWIR range, as it can be manufactured on
low cost InP substrates in a mainstream technology for optical telecommunications. By removing the substrate the
spectral range can be extended to the [0.6 - 1.7 μm] range. In this way low cost, room temperature operated FPAs
cameras for imaging and hyperspectral applications can be developed. The FPA is built around a low power CTIA stage
with 3 S&H capacitors in the 20*20 um2 unit cell. This approach results in a synchronous shutter operation, which will
support both ITR and IWR operation.
In IWR mode the integration dead time is limited to max. 10 μsec. The CDS operation yields in a high sensitivity
combined with a low noise: This presentation will focus on the development of a 20 μm pitch 320*256 device, with the
following main characteristics: 20 μV/e-sensitivity and < 60 e-noise. The 4 low-power, differential outputs are enabling
to drive an output load of > 30 pF at 40 Msamples/sec each, resulting in a > 1700 Hz frame rate, while at the same time
the overall nominal power dissipation is < 200 mW. The ROIC is realized in a 0.35 um technology and the outputs are
designed to drive directly a 3.3 V, 1.5 V VCM differential AD convertor. The circuit also supports a NDR operating
mode to further reduce the noise of the FPA. A small from factor camera with Cameralink output is built around this
A high resolution, high frame rate InGaAs based image sensor and associated camera has been developed. The sensor
and the camera are capable of recording and delivering more than 1700 full 640x512pixel frames per second.
The FPA utilizes a low lag CTIA current integrator in each pixel, enabling integration times shorter than one
microsecond. On-chip logics allows for four different sub windows to be read out simultaneously at even higher rates.
The spectral sensitivity of the FPA is situated in the SWIR range [0.9-1.7 µm] and can be further extended into the
Visible and NIR range.
The Cheetah camera has max 16 GB of on-board memory to store the acquired images and transfer the data over a
Gigabit Ethernet connection to the PC. The camera is also equipped with a full CameralinkTM interface to directly
stream the data to a frame grabber or dedicated image processing unit. The Cheetah camera is completely under