Broadband analog to digital conversion with spatial-spectral holography

Babbitt, W.R.; Neifeld, Mark A.; Merkel, K.D.

doi:10.1016/j.jlumin.2007.02.018

Cited by 10 publications

(10 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The modified absorption spectrum can be characterized by an average modified absorption coefficient spectrum, given to first order in the power spectrum by [2] …”

Section: Spatial-spectral Holographymentioning

confidence: 99%

Digitization of Microwave Signals with Spatial Spectral Holography

Babbitt

2007

OFC/NFOEC 2007 - 2007 Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference

View full text Add to dashboard Cite

A new optical approach to broadband analog-to-digital conversion is discussed, which directly records signals in the frequency domain. This frequency-domain stretch processor can achieve 10-bit performance at 20GSPS and is extendable to signals over 100GHz. IntroductionModern radar, communications, and processing systems require both precise generation and digital capture of complex microwave arbitrary waveforms. Spatial spectral holography (SSH), the recording and readout of spectral gratings in inhomogeneously broadened absorbers, can be applied to both these needs. The ability of SSH to produce arbitrary waveforms has been demonstrated up to a few gigahertz,[1] and existing SSH materials hold the potential for producing arbitrary waveforms with bandwidths over 300 GHz with time-bandwidth products (TBP) (the waveform duration multiplied by its bandwidth) over 10 6 . The application of SSH to analog to digital conversion has only recently been proposed,[2] yet SSH technology holds the promise of capturing signals at 20 GSPS with over 10 bits of vertical resolution in the near term with existing components and materials. Electronic ADCs are currently limited to fewer than 7 effective resolution bits when operating above 10 GHz.[3] SSH ADC also have a clear path to the capture of signals at over 100 GSPS, plus several other attractive attributes.The SSH ADC is in the class of photonic-assisted ADCs, which work by first modulating high bandwidth electronic signals onto optical carriers before using optical techniques to achieve high dynamic range digitization. An example is time-stretched waveform processing, where a microwave waveform is intensity modulated onto a frequency chirped optical pulse. The modulated pulse is stretched by a highly dispersive element, which reduces the pulse's intensity modulation bandwidth, enabling its digitization with a lower bandwidth high performance electronic ADC. Unfortunately, bandwidth enhancements (time-stretch factors) significantly greater than 10 and TBPs significantly greater than 1000 are difficult to achieve with current devices, limiting applicability. [4] The SSH-ADC utilizes a new paradigm in signal stretching. Rather than stretching a signal in the time-domain, the SSH-ADC stretches a signal's frequency domain representation. This is possible due to the unique properties of spatial-spectral holographic (SSH) materials. [5,6] Like time-stretch processors, the SSH-ADC exploits the high performance of lower bandwidth ADCs. SSH-ADCs can achieve bandwidths and TBPs that are several orders of magnitude greater than optical time-stretching techniques. Simulations predict SSH-ADCs can achieve greater than 10 effective resolution bits at 20 GSPS. Currently available materials support bandwidths over 100 GHz. Spatial-Spectral HolographySSH materials are unique in their ability to act as broadband spectral recording devices with ultra-fine frequency resolution (large TBPs).[5] The ultra-fine frequency resolution of a SSH material arises from the intrinsic homogeneous linewidth ...

show abstract

“…The modified absorption spectrum can be characterized by an average modified absorption coefficient spectrum, given to first order in the power spectrum by [2] …”

Section: Spatial-spectral Holographymentioning

confidence: 99%

Digitization of Microwave Signals with Spatial Spectral Holography

Babbitt

2007

OFC/NFOEC 2007 - 2007 Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference

View full text Add to dashboard Cite

show abstract

“…Recently an approach to photonics assisted ADC has been proposed [4], which utilizes spatial spectral holography (SSH) in inhomogeneously broadened optical absorbers. Simulations have shown that this approach could provide direct conversion of signals at 20 GSPS with over 10 bits of vertical resolution in the near term with existing components and materials.…”

Section: Introductionmentioning

confidence: 99%

“…The SSH material responds to a broadband optical signal by recording a high-fidelity replica of its power spectrum in the form of a modified absorption spectrum, which persists for several milliseconds, allowing time for frequency domain readout. The SSH-ADC operates in essentially two steps [4], as illustrated in Figure 1 Readout: a chirped optical waveform reads the absorption profile, which is detected and digitized with high fidelity, low speed ADCs, and post processed to yield the digitized version of the SOI. SSH material.…”

Section: Introductionmentioning

confidence: 99%

“…To achieve this, a dual capture technique is utilized, which records the SOI simultaneously with a pair of complementary codes [4,6]. The addition of the autocorrelations of such complementary codes results in sidelobe free (perfect delta function) performance, and similarly for the SSH-ADC, the addition of the two independent captures results in faithful reproduction of the SOI.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Demonstration of Analog-to-Digital Conversion Using Spatial-Spectral Holography

Reibel

Harrington

Dahl

et al. 2008

OFC/NFOEC 2008 - 2008 Conference on Optical Fiber Communication/National Fiber Optic Engineers Conference

View full text Add to dashboard Cite

Proof-of-concept demonstrations for an optical approach to broadband analog-to-digital conversion are shown with 800 MHz bandwidth and >26dB dynamic range. Models suggest that this frequency-domain stretched processor could achieve 10-bit performance over 20 GHz bandwidths.OCIS codes: (070.1170) Analog optical signal processing; (090.2900) Optical storage materials IntroductionWith the advent of software defined radios, ultra-wideband communication protocols, and extremely high frequency carriers (>90 GHz), modern microwave systems are becoming more complex and diverse. In addition to flexible carrier frequency and modulation formats, microwave systems continue to increase their signal bandwidths for enhanced performance. While electronic analog-to-digital converters (ADCs) have seen steady improvement in performance over the past several years, there are still no single chip ADCs that can directly capture signals with 10 effective vertical bits of resolution beyond 2 GHz of bandwidth. The tracking of single chip ADC performance improvements over the past several years has shown that only modest improvements in performance can be expected in the near term [1]. Due to this, there has been an increased interest in photonic based ADC systems [2], to try to enhance signal capture bandwidths and vertical resolution. In particular, photonic-assisted ADCs have shown significant promise arising from the capability to modulate high bandwidth electronic signals directly onto an optical carrier and to utilize lower bandwidth digitizers with high dynamic range. Recently, time-stretch photonic assisted ADCs have shown effective sampling rates in excess of 1 terasample per second with 5 vertical bits of resolution [3], however, time apertures remain limited due to time bandwidth product (TBP) limitations.Recently an approach to photonics assisted ADC has been proposed [4], which utilizes spatial spectral holography (SSH) in inhomogeneously broadened optical absorbers. Simulations have shown that this approach could provide direct conversion of signals at 20 GSPS with over 10 bits of vertical resolution in the near term with existing components and materials. This approach may also be extendable to bandwidths over 300 GHz in newly available materials. Rather than stretching a signal in the time-domain, the SSH-ADC stretches a signal's frequency domain representation. Like time-stretched processors, the SSH-ADC exploits the high performance of lower bandwidth ADCs and wide bandwidth telecom grade modulators. However, the potential TBP of the SSH-ADC is several orders of magnitude greater than currently demonstrated optical time-stretching techniques. This paper presents the first ever proof-of-concept demonstrations of the SSH-ADC technique on signals with equipment limited bandwidths up to 800 MHz and >26 dB of dynamic range (4.4 vertical bits). These demonstrations also show the system's ability to provide direct digitization of signals with large 6.5 GHz microwave carrier frequencies.2. Spatial-Spectral Holographic Analog-to-...

show abstract

“…The S2 optical materials comprised of rare-earth ions doped into crystalline hosts exhibit ultra-wide inhomogeneous spectral absorption features that are composed of many narrow homogeneous linewidth absorptions. In a single spatial volume (typically a 1 cm long, 100 mm diameter cylinder), these materials can accommodate hundreds of GHz of processing bandwidth with sub-MHz resolution [3] when cryogenically cooled to 4 K. S2 material-based analog optical signal processing devices are being developed for numerous applications including real-time wideband range-Doppler radar using arbitrary waveforms [4,5], real-time wideband spectral analysis for signal intelligence and networking in extreme environments [6][7][8][9], and photonic A/D conversion [10]. The advantage of these real-time processing devices is their ability to process high-time-bandwidth product signals, store the result, then allow an optical linear frequency modulated waveform (LFM) to extract the result [11,12] at a reduced bandwidth allowing the use of low-bandwidth high-dynamic-range photodetectors and digitizers.…”

Section: Introductionmentioning

confidence: 99%