## 1 Introduction  
Semoconductor photo-detectors are devices that can convert optical signals into electronic signals, and they are extensively used in optical communication systems [1]. Ideally a photo-detector should detect all the incident light, respond to the fastest changes in the incoming signal and not introduce additional noise. In practice, photo-detectors have limited bandwidth with finite response times, they have associated noise sources and the probability of detecting an individual photon of light is less than one. Furthermore, photo-detectors have tradeoffs particularly between speed (bandwidth) and quantum efficiency, whereby designs are aimed to increase their bandwidth-efficiency product [1]. Several types of detectors can be used in fiber optic systems for communications, sensing and measurement systems. Some of the most common types include _p-i-n_ photodiodes, metal semiconductor metal photodiodes and avalanche photodiodes [1]. Alternatives to traditional photo-detectors include optical control of microwave devices for generation of high-speed low-phase noise oscillations. Injection locking of optically controlled microwave oscillators allows synchronizing the frequency and phase of free-running oscillators to optical modulated signals and can find extensive applications, ranging from wireless communications [2] to high-speed optical communications such as radio-over-fiber networks [3, 4], from bio-imaging for identifying cancers [5] to test instruments. Direct optical control of microwave devices has been investigated in Gunn oscillators [6], tuning and power modulation of trapped plasma avalanche and transit time (TRAPATT) oscillators [7], and tuning of impact avalanche and transit time (IMPATT) oscillators [8]. However, these devices are limited in bandwidth and not amenable to integrated circuit realization and, because of nature of the processes involved, they require inconveniently high bias voltages, for example the avalanche effect is noisy and can introduce additional timing jitter and phase noise resulting in considerable inferior stability. Currently, many researchers are looking for solutions to cleanly transfer the stability of high quality (_Q_) optical signals to microwave electronic signals. The proposed configurations employ either direct or external modulation of laser diodes ([9], and references therein), or heterojunction bipolar transistors (HBTs) [10], among others [11]. However, most of these schemes require several electronic and optoelectronic components such as phase-locked local oscillators, amplifiers, photo-detectors, light emitters, and/or amplifiers or modulators, which make them rather complex and costly for applications where compact solutions for the transmission and distribution of radio-frequency (RF) signals are needed [11]. Recently, optical injection locking of double barrier quantum well (DBQW) resonant tunneling diode (RTD) photo-detector devices to intensity modulated optical signals [12, 13], and self-injection locking of a low cost, simple and compact RTD optoelectronic oscillator (OEO) configuration [14, 15] have been successfully demonstrated that could substantially increase the practicality of optically controlled microwave oscillators for a wider range of microwave and photonics applications. In this article, DBQW-RTD based optical waveguide photo-detectors are described for the implementation of novel optically injection locked microwave oscillators that are controlled using signals at telecommunications wavelengths for applications in clock recovery and fiber optic based communication systems. The photodetection results show the noise of the microwave injection locked RTD signal matches that of the input optical analogue and digital signals resulting in low timing jitter of the electrically detected carrier signal.