Novel tone-like polarization modulation-based encoding method experimental demonstrated on a 10 G data channel over 130 Km

Abstract

We present a novel encoding method and feasibility demonstration using tone-like polarization modulation onto an independently modulated optical signal for supervisory signaling within optical networks. We demonstrate experimentally error free performance for 10Gbps NRZ and 155Mbs polarization modulated signal. IntroductionIn long-haul systems, polarization effects within a network are usually minimized by the type and the length of a given fiber type, specific polarization-related component specifications (e.g. polarization dependent gain and loss), and the use of polarization dispersion compensators. Regardless of this, however, the state of polarization (SOP) of optical signals traveling in a fiber is still known to change because of fluctuations in fiber temperature, stress, or strain. However, such events are more likely to occur in terrestrial networks where mechanical disturbances due to the external influences (i.e. human activity) can occur. In fact, studies of undersea fiber optic transmission links have shown that the SOP changes are slowly varying, changing on the order of minutes to hours [1,2,3]. Various polarization control techniques have been developed to monitor and correct these slow varying SOP variations [4]. The SOP of a transoceanic optical signal has actually been tracked by using a polarization tracking receiver [9] and it has been demonstrated that polarization control can be performed at a receiver [4,5,9] as long as depolarization and nonlinear polarization conversion have not occurred. The result of this ability to control the SOP at the receiver allows polarization modulation to be used as an information carrier that is in addition to conventional detection schemes. Such a transmission approach can possibly be used as a low data rate protection trigger between optical network protection elements[6], or a provisioning method between end terminals and remote network elements. Compatible with this approach are the numerous polarization modulation techniques that have been demonstrated in materials such as GaAs and lithium niobate and have been shown to be relatively simple to implement [7,8]. A method to encode a high speed optical signal with a low data rate polarization encoded tone-like modulated signal is demonstrated here. The design of the proposed polarization encoder/decoder and the bit sequencing of the underlying data stream are discussed, and the results of transmission of polarization modulation on a 10Gbps signal in a 136km transmission link is described. We show that the error-free IOG NRZ signal quality is not affected by the encoded polarization modulation and that the 155Mbps polarization modulated signal can be successfully recovered simultaneously.