Millimeter-wave Generation Scheme Research Articles

A simplified optical millimeter-wave generation scheme based on frequency-quadrupling

This paper analyzes and demonstrates a simplified frequency quadrupling configuration for optical millimeter-wave (mm-wave) generation, in which the electrical phase shifter and optical filter are omitted. Theoretical analysis is given to reach the optimum operating conditions including direct current (DC) bias voltage, optical transmission point of the dual-parallel Mach-Zehnder modulator (MZM) bias voltage, optical transmission point of the dual-parallel Mach-Zehnder modulator (DP-MZM), amplitude of the radio frequency (RF) driving signal and the impact of the extinction ratio (EF) on the optical sideband suppression ratio (OSSR) and radio frequency spurious suppression ratio (RFSSR). Experiments prove an OSSR of 15 dB and an RFSSR of 26 dB for the new frequency quadrupling scheme at 6 GHz, 8GHz and 10 GHz of RF driving signal without any electrical phase shifter or optical filter. This system exhibits the advantage of low wavelength dependence and large frequency tunable range.

Energy efficient photonic millimeter-wave generation using cascaded polarization modulators

A filter-less millimeter-wave generation scheme consisting of four polarization modulators in series, each followed by a polarizer is proposed to achieve optoelectronic frequency octupling. The cascade of polarization modulator and polarizer provides an intensity modulator whose biasing condition can be set by the polarizer angle and polarization state of the input light to each polarization modulator. A theoretical analysis of the architecture is performed using a transfer function method and validated by industry-standard software simulation tools. The circuit shows high potential in achieving desired performance with lower input RF power when compared to the another configuration based on a generalized Mach–Zehnder interferometer structure. Although the operating range in terms of applied RF drive becomes narrow, low RF input operation can be achieved by this circuit. The effect of imbalances in the key circuit parameters is also investigated in terms of electrical side harmonic suppression ratio.

Comments on, Xuan Li, Shanghong Zhao, Zihang Zhu, Bing Gong, Xingchun Chu, Yongjun Li, Jing Zhao and Yun Liu ‘an optical millimeter-wave generation scheme based on two parallel dual-parallel Mach–Zehnder modulators and polarization multiplexing’, Journal of Modern Optics, 2015

In the title paper, Li et al. have presented a scheme for filter-less photonic millimetre-wave (mm-wave) generation based on two polarization multiplexed parallel dual-parallel Mach–Zehnder modulators (DP-MZMs). For frequency octo-tupling, all the harmonics are suppressed except those of order 4l, where l is the integer. The carrier is then suppressed by the polarization multiplexing technique, which is the principal innovative step in their design. Frequency 12-tupling and 16-tupling is also described following a similar method. The two DP-MZM are similarly driven and provide identical outputs for the same RF modulation indices. Consequently, a demerit of their design is the requirement to apply two different RF signal modulation indexes in a particular range and set the polarizer to a precise angle which depends on the pair of modulation indices used in order to suppress the unwanted harmonics (e.g. the carrier) without simultaneously suppressing the wanted harmonics. The aim of this comment is to show that, an adjustment of the RF drive phases with a fixed polarizer angle with the design presented by Li, all harmonics can be suppressed except those of order4l, where l is an odd integer. Hence, a filter-less frequency octo-tupling can be generated whose performance is not limited by the careful adjustment of the RF drive signal, rather it can be operated for a wide range of modulation indexes (m ~ 2.5 → 7.5). If the modulation index is adjusted to suppress 4th harmonics, then the design can be used to perform frequency 24-tupling. Since, the carrier is suppressed by design in the modified architecture, the strict requirement to adjust the RF drive (and polarizer angle) can be avoided without any significant change to the circuit complexity.

An Optical Millimeter-Wave Generator Using Optical Higher Order Sideband Injection Locking in a Fabry–Pérot Laser Diode

We proposed an optical millimeter-wave generator using a directly modulated optical injection-locked Fabry–Perot laser diode (FP-LD). In the proposed scheme, one of the higher order sidebands of the master laser light, which is generated by modulation of the bias current of the slave FP-LD, is used to injection-lock one of the FP-LD cavity modes. Low-phase noise millimeter wave is generated through the beating of the injection-locked FP-LD output and the injected master laser light. The proposed scheme does not require an external modulator, high-bandwidth devices, strong external optical injection power, or an additional optical filter. The effects of the choice of lower or upper sideband for injection locking, optical injection power, and amplitudes of the ac and dc components of the bias current on the proposed optical millimeter-wave generation scheme are studied. An experimental testbed is also built to realize the proposed optical millimeter-wave generation and its distribution in radio-over-fiber systems.

An optical millimeter-wave generation scheme based on two parallel dual-parallel Mach–Zehnder modulators and polarization multiplexing

A novel filterless optical millimeter-wave signal generation scheme is proposed. In the scheme, the undesired sidebands are suppressed using two parallel dual-parallel Mach–Zehnder modulators (MZMs) with different modulation indexes and polarization multiplexing, and frequency multiplication factor as high as 16 can be achieved. Simulation results show that 80, 120, and 160 GHz signals are generated through a 10 GHz RF signal using the proposed method, and the performance of the generated signals is good when commercially available MZMs with extinction ratio of 20–30 dB are used. The scheme has large tunability of modulation index for frequency octupling and 12-tupling signals generation and high stability against the RF driving voltage deviation for frequency 16-tupling generation.

Comments on X. Yin, A. Wen, Y. Chen, and T. Wang, ‘Studies in an optical millimeter-wave generation scheme via two parallel dual-parallel Mach–Zehnder modulators’, Journal of Modern Optics, 58(8), 2011, pp. 665–673

Yin et al. have described an innovative filter-less optical millimeter-wave generation scheme for octotupling of a 10 GHz RF oscillator, or sedecimtupling of a 5 GHz RF oscillator using two parallel dual-parallel Mach–Zehnder modulators (DP-MZMs). The great merit of their design is the suppression of all harmonics except those of order (octotupling) or all harmonics except those of order (sedecimtupling), where is an integer. A demerit of their scheme is the requirement to set a precise RF signal modulation index in order to suppress the zeroth order optical carrier. The purpose of this comment is to show that, in the case of the octotupling function, all harmonics may be suppressed except those of order , where is an odd integer, by the simple addition of an optical phase shift between the two DP-MZMs and an adjustment of the RF drive phases. Since the carrier is suppressed in the modified architecture, the octotupling circuit is thereby released of the strict requirement to set the drive level to a precise value without any significant increase in circuit complexity.

A novel OCS millimeter-wave generation scheme with data carried only by one sideband and wavelength reuse for uplink connection

We propose a novel optical carrier suppression (OCS) millimeter-wave generation scheme with data carried only by one sideband using a dual-drive Mach–Zehnder modulator (MZM) in radio-over-fiber system, and the transmission performance is also investigated. As the signal is transmitted along the fiber, there is no time shifting of the codes caused by chromatic dispersion. Simulation results show that the eye diagram keeps open and clear even when the optical millimeter-waves are transmitted over 110km and the power penalty is about 1.9dB after fiber transmission distance of 60km. Furthermore, due to the +1 order sideband carrying no data, a full duplex radio-over-fiber link based on wavelength reuse is also built to simplify the base station. The bidirectional 2.5Gbit/s data is successfully transmitted over a 40km standard single mode fiber with less than 0.8dB power penalty in the simulation. Both theoretical analysis and simulation results show that our scheme is feasible and we can obtain a simple cost-efficient configuration and good performance over long-distance transmission.

Studies in an optical millimeter-wave generation scheme via two parallel dual-parallel Mach–Zehnder modulators

A novel filterless optical millimeter-wave generation scheme via two parallel dual-parallel Mach–Zehnder modulators (MZMs) is proposed. Theoretical analysis suggests that it can be used for the generation of millimeter-wave signal with octupling or 16-tupling of the local oscillator. An 80 GHz millimeter-wave is generated by octupling of a 10 GHz RF oscillator, or 16-tupling of a 5 GHz RF oscillator. Several influence factors on the performance of the optical sideband suppression ratio (OSSR) and the radio frequency spurious suppression ratio (RFSSR) are numerically studied. Simulation results show that the generated millimeter-wave can keep good performance, especially for octupling millimeter-wave generation; its performance is stable and insensitive to the extinction ratio of MZMs and the DC bias drift.

Multiband 60-GHz Wireless Over Fiber Access System With High Dispersion Tolerance Using Frequency Tripling Technique

A new optical millimeter-wave generation scheme to triple the beating frequency based on subcarrier multiplexing in combination with single sideband technique is proposed, capable of high tolerance of fiber chromatic dispersion. The proposed scheme can be applied to two types of multiband 60-GHz wireless over fiber access systems: one with widely separated bands including millimeter-wave, microwave and baseband and the other one with multiple 60-GHz sub-bands. Experimental verification of the proposed system with widely separated bands is presented with the generation and error-free transmission of 2.1-Gb/s data on the 63-GHz mm-wave and 21-GHz microwave carriers over 50-km single-mode fiber (SMF-28) without dispersion compensation. The power penalties caused by 50-km fiber transmission for both signals are both less than 1.0 dB at BER of 10-9 Meanwhile, simultaneous generation and transmission of multiple services at 60-GHz sub-bands are also introduced. The experimental results demonstrate the successful delivery of the 1-Gbps data carried by 60-GHz millimeter-wave both over 50-km SMF-28 and wireless distance of 6-m without any dispersion compensation. The optical receiver sensitivity of the transmission with two sub-bands degrades by 2 dB compared with the single band 60-GHz signal, and the power penalty from 50-km SMF-28 transmission is 0.8 dB at BER of 10-9. From the theoretical analysis and experimental demonstrations of the two multiband systems, it is concluded that the proposed millimeter-wave generation scheme indeed increase the transmission distance for the system with 60-GHz signal, which normally having SMF transmission distance of few tens of kilometers, by utilizing optical and electrical components with low-bandwidth requirements.

Optical Millimeter-Wave Generation and Transmission Without Carrier Suppression for Single- and Multi-Band Wireless Over Fiber Applications

A new optical millimeter-wave generation scheme to double the beating frequency without suppressing the carrier by taking advantages of the out-of-phase property between sidebands of a phase-modulated optical carrier is proposed for the first time. Theoretical analysis shows that the generated 60 GHz optical millimeter-wave (mm-wave) can tolerant ±0.016 nm wavelength drifting with filter bandwidth ranging from 70 to 100 GHz to sustain first to second harmonic suppression ratio of 18 dB. The doubled frequency is continuously tunable from 60 to 90 GHz within 100 GHz filter bandwidth with RF power variation of less than 2 dB. In addition, simultaneously generating and transmitting multi-band signal: millimeter-wave band, microwave band, and baseband leveraging the same concept is also proposed. Error-free transmission of 2.5 Gb/s wireless baseband signals carried by the generated 60 GHz mm-wave is successfully demonstrated in both single- and multi-band network environments over a combined optical fiber and wireless distance with a proper equivalent isotropically radiated power of about 20 dBm for in-building access. Moreover, dispersion effect on the generated frequency-doubled optical mm-wave is analyzed by experimentally comparing the link performance of both single mode fiber (SMF-28) and dispersion-shifted fiber cases. It is concluded that for single-band service delivery, the proposed scheme is immune to the interference from the dispersion-induced, redundant 1st harmonics; however, to deliver multi-band services, launching lightwave at zero-dispersion wavelength over SMF-28 is highly recommended to mitigate inter-band interference.