Adaptive Optical Splitter Employing an Opto-VLSI Processor and a 4-$f$ Imaging System

A novel adaptive optical splitter structure employing an Opto-VLSI processor and 4-f imaging system is proposed and experimentally demonstrated. By driving the Opto-VLSI processor with computer generated multicasting phase holograms, an input optical signal launched into an input optical fiber port can be split and coupled into many output optical fiber ports with arbitrary splitting ratios. A proof-of-principle 1 × 2 adaptive optical splitter structure driven by optimized multicasting phase holograms uploaded onto the Opto-VLSI processor is developed, demonstrating an arbitrary splitting ratio over a wavelength range exceeding 50 nm.

I. Introduction

The demand for optical power splitters is growing globally, due to the rapid deployment of fiber-to-the-premises (FTTP), optical metropolitan area network (MAN), and active optical cables for TV/Video signal transport [1]. Passive optical network (PON) technology enables several hundred users to share one optical line terminal (OLT) at the central office distributing optical power to several tens of optical network units (ONUs) at the customer end of the network, each of which is shared by many users [2]. However, current PONs, which use fixed optical power splitters, have limited reconfigurability not only to adding/dropping users to/from an ONU but also to changing services for each user. An adaptive optical power splitter can dynamically reallocate the optical power in the entire network according to the real-time distribution of users and services, thus providing numerous advantages such as improvement of optical network efficiency and network scalability, and high network reliability. An adaptive optical power splitter is also necessary for implementing a self-healing ring in a MAN [3], which offers a popular protection mode that automatically recovers communication from failure. Furthermore, future optical line protection (OLP) systems require adaptive optical splitters to: i) transfer the optical power from the primary path to the secondary path dynamically; ii) avoid the use of optical power attenuators and optical amplifiers; and iii) monitor both paths instantaneously [4]. Moreover, adaptive optical power splitters can add many advantages into fiber CATV networks, including substantial improvement in network adaptability and scalability [5].