5 Gbps wireless transmission link with an optically pumped uni-traveling carrier photodiode mixer at the receiver

We report the first demonstration of a uni-traveling carrier photodiode (UTC-PD) used as a 5 Gbps wireless receiver. In this experiment, a 35.1 GHz carrier was electrically modulated with 5 Gbps non-return with zero on-off keying (NRZ–OOK) data and transmitted wirelessly over a distance of 1.3 m. At the receiver, a UTC-PD was used as an optically pumped mixer (OPM) to down-convert the received radio frequency (RF) signal to an intermediate frequency (IF) of 11.7 GHz, before it was down-converted to the baseband using an electronic mixer. The recovered data show a clear eye diagram, and a bit error rate (BER) of less than 10 −8 was measured. The conversion loss of the UTC-PD optoelectronic mixer has been measured at 22 dB. The frequency of the local oscillator (LO) used for the UTC-PD is defined by the frequency spacing between the two optical tones, which can be broadly tuneable offering the frequency agility of this photodiode-based receiver

Optical Phase Lock Loop as High-Quality Tuneable Filter for Optical Frequency Comb Line Selection

This paper describes an optical phase lock loop (OPLL) implemented as an ultraselective optical frequency comb line filter. The OPLL is based on a photonic integrated circuit (PIC) fabricated for the first time through a generic foundry approach. The PIC contains a distributed Bragg reflector (DBR) laser whose frequency and phase are stabilized by reference to an optical frequency comb generator. The OPLL output is a single-mode DBR laser line; other comb lines and noise at the output of the OPLL filter are attenuated by >58 dB below the peak power of the OPLLfilter output line. The OPLL bandwidth is up to 200 MHz, giving a filter quality factor greater than 1,000,000. The DBR laser can be tuned over 1 THz (8 nm), enabling different comb lines to be selected. Locking to a comb line with a frequency offset precisely selectable between 4 and 12 GHz is also possible. The coherence between the DBR laser and the comb lines is demonstrated by measurements of the heterodyne signal residual phase noise level, which is below −100 dBc/Hz at 5 kHz offset from the carrier. The OPLL-filter output can be up to 6 dB higher than the peak power of the comb line to be isolated by the filter. This optical gain is a unique characteristic which can significantly improve the SNR of communication or spectroscopy systems. This OPLL is envisaged to be used for high purity, tuneable microwave, millimetre-wave, and THz generation

Photonic integrated circuit optical phase lock loop tuneable active filter

We report the first foundry-fabricated photonic integrated circuit (PIC) optical phase lock loop (OPLL) tuneable active optical filter for optical frequency comb line selection and amplification. The PIC containing DBR lasers and photodiodes is integrated with low frequency electronics to create an OPLL, which functions as a highly selective optical filter with sub-GHz bandwidth and 50dB out-of-band suppression. The OPLL output is a single tone coherent with the comb line, whose optical power is 6dB higher than the selected input line, and whose frequency can be offset from the input line by an agile and precisely defined frequency

Optical phase lock loop as high-Q filter for optical frequency comb line selection

This paper describes the first optical phase lock loop (OPLL) based on a photonic integrated circuit (PIC) fabricated using a generic foundry process and off-the-shelf electronic components. The PIC contains a DBR laser that is for the first time frequency and phase stabilized in reference to an Optical Frequency Comb Generator (OFCG) line. The OFCG used in this demonstration offers 19 highly coherent lines spaced by 15 GHz. The OPLL can attenuate all adjacent comb lines and noise by more than 50 dB below the power of the selected comb line. Hence, the OPLL can be considered as an ultra-selective optical filter. The OPLL output is a single mode DBR laser line, with frequency offset from the reference comb line exactly selectable over the frequency range 4 GHz to 12 GHz. The laser can be current tuned over a 1 THz (8 nm) range enabling the different comb lines to be selected. The coherence between DBR laser and comb lines is demonstrated by measurements of the heterodyne signal residual phase noise level, which is below -100 dBc/Hz at 5 kHz offsets from the carrier. This is a record low value for an OPLL based on a monolithically photonic integrated circuit. Such an OPLL could be used for high purity, tuneable millimetre and THz wave generation

Coherent Frequency Tuneable THz Wireless Signal Generation Using an Optical Phase Lock Loop System

We demonstrate experimentally, for the first time, the photonic generation of a continuous tunable THz wireless signal based on using an optical phase lock loop (OPLL) subsystem and optical frequency comb generator (OFCG). The OPLL is employed to select one line from the optical comb and shift it by the desired frequency offset allowing for the frequency tuneability of THz carrier signal. The selected optical tone from the OPLL is heterodyne mixed with another selected optical line of the optical comb to generate a stabilized THz frequency carrier with a low phase noise. Full system operation is demonstrated by transmitting wirelessly a THz signal modulated with 10 Gbaud QPSK data. The system evaluation is carried out for four selected THz carrier frequencies obtained by tuning the laser included in the OPLL. This configuration is a promising architecture that would allow a THz carrier to be flexibly generated at the central office with high frequency stability and low phase noise

1 Gbaud QPSK Wireless Receiver using an Opto-Electronic Mixer

This paper presents the first demonstration of a uni-travelling carrier photodiode (UTC-PD) used as a receiver of a wirelessly transmitted quadrature phase shift keying (QPSK) signal. In this demonstration, a 1 Gbaud QPSK signal centered at 33.5 GHz was transmitted over a wireless distance of 1.4 m. At the receiver, a UTC-PD is used to down-convert the RF signal to an intermediate frequency (IF) of 9.5 GHz by mixing the RF signal with a heterodyne signal at 24 GHz. The down-converted signal is captured by a real time digital oscilloscope for further digital signal processing. The error vector magnitude (EVM) of the demodulated signal was measured to be 18%, which corresponds to a bit error rate (BER) of 10-8

Optical Frequency Tuning for Coherent THz Wireless Signals

OAPACRWN THz wireless signals have become of interest for future broadband wireless communication. In a scenario where the wireless signals are distributed to many small remote antenna units (RAUs), this will require systems which allow flexible frequency tuning of the generated THz carrier. In this paper, we demonstrate experimentally the implementation of two tuning methods using an optical frequency comb generator (OFCG) for coherent optical frequency tuning in THz wireless-over-fiber systems. The first method is based on using a photonic integrated circuit optical phase lock loop (OPLL) sub-system implemented as a high quality optical filter for single comb line selection and optical amplification. The OPLL generates an optical carrier which is frequency and phase stabilized in reference to one of the optical comb lines with a frequency offset precisely selectable between 4 GHz and 12 GHz. The second method is based on optical single sideband suppressed carrier (SSB-SC) modulation from the filtered comb line using an optical IQ modulator. With this technique, it is possible to suppress the other unwanted optical tones by more than 40 dB. This generated optical carrier is then heterodyned with another filtered optical comb line to generate a tuneable and stable THz carrier. The full system implementations for both methods are demonstrated by transmitting THz wireless signal over fiber with 20 Gbps data in QPSK modulation. The system performance and the quality of the generated THz carrier are evaluated for both methods at different tuned THz carrier frequencies. The methods demonstrated confirm that a high quality tuneable THz carrier can easily be implemented in systems where dynamic frequency allocation is required

Photonic systems for tunable mm-wave and THz wireless communications

In this paper we present two different techniques for photonic generation of millimeter and THz waves. Each of them tackles the phase noise problem associated with optical sources in a different way. The first one relays on the heterodyne down-conversion of two phase noise correlated optical tones. The correlation is achieved by generation of an optical frequency comb. To select one of the optical lines we use an optical phase lock loop, which besides enabling a frequency offset between output and input, can provide optical gain and is highly selective. The second one relays on the envelope detection of a single sideband-with carrier signal. In this approach the photonic remote antenna unit is implemented as monolithically integrated photonic chip

60 GHz Wireless Link Implementing an Electronic Mixer Driven by a Photonically Integrated Uni-Traveling Carrier Photodiode at the Receiver

We report the first 60 GHz wireless link implementing a uni-traveling carrier photodiode (UTC-PD) at the transmitter and a photonic integrated chip incorporating a UTC-PD at the receiver. In this demonstration, a 64.5 GHz signal carrying 1 Gbps on-off keying (OOK) data was generated by heterodyning two optical tones into the transmitter UTC-PD. The signal was transmitted using a 24 dBi gain parabolic antenna over a wireless distance of three metres before reaching an identical receiver antenna. At the receiver, an electronic mixer was used to down-convert the received signal into an intermediate frequency of 12.5 GHz. The local oscillator to the electronic mixer was provided by heterodyne mixing of two optical tones generated using a UTC-PD that is monolithically integrated with semiconductor lasers. The down-converted signal was acquired by a real-time oscilloscope for offline processing, which showed zero error bits in a 10 5 bit-long transmission

Genome editing reveals a role for OCT4 in human embryogenesis.

Despite their fundamental biological and clinical importance, the molecular mechanisms that regulate the first cell fate decisions in the human embryo are not well understood. Here we use CRISPR-Cas9-mediated genome editing to investigate the function of the pluripotency transcription factor OCT4 during human embryogenesis. We identified an efficient OCT4-targeting guide RNA using an inducible human embryonic stem cell-based system and microinjection of mouse zygotes. Using these refined methods, we efficiently and specifically targeted the gene encoding OCT4 (POU5F1) in diploid human zygotes and found that blastocyst development was compromised. Transcriptomics analysis revealed that, in POU5F1-null cells, gene expression was downregulated not only for extra-embryonic trophectoderm genes, such as CDX2, but also for regulators of the pluripotent epiblast, including NANOG. By contrast, Pou5f1-null mouse embryos maintained the expression of orthologous genes, and blastocyst development was established, but maintenance was compromised. We conclude that CRISPR-Cas9-mediated genome editing is a powerful method for investigating gene function in the context of human development.DW was supported by the National Institute for Health Research (NIHR) Oxford Biomedical Research Centre Programme. NK was supported by the University of Oxford Clarendon Fund. AB was supported by a British Heart Foundation PhD Studentship (FS/11/77/39327). LV was supported by core grant funding from the Wellcome Trust and Medical Research Council (PSAG028). J-SK was supported by the Institute for Basic Science (IBS-R021-D1). Work in the KKN and JMAT labs was supported by the Francis Crick Institute which receives its core funding from Cancer Research UK, the UK Medical Research Council, and the Wellcome Trust (FC001120 and FC001193)