Broadband Exchange by Coherent Multi - Carrier Switching E. -J. Bachus, R.- P.Braun, C.Caspar, H.M.Foisel, N.Keil, H.H.Yao and B.Strebel Heinrich -Hertz -Institut für Nachrichtentechnik Berlin GmbH Einsteinufer 37, D -1000 Berlin 10, FRG ABSTRACT A proposed high capacity optical Coherent Multi- Carrier (CMC) switching node for broad- band application is described. The switching of signals is performed in the optical domain by routing the carriers through broadband and selective stars, by frequency conversion and tunable heterodyn- receivers. Experimental results of a switching element are presented and a simple calculation shows, that more than 10,000 broadband carriers could be processed. INTRODUCTION Frequency -multiplex techniques are applied in radio- and microwave - communication links if the bandwidth of the transmission medium is much higher than the bandwidth of a single signal. This is particularly the case in fiber -optic transmission and consequently the investigations in the field of High- Density -Wavelength- Division Multiplex techniques ( HDWDM) and Coherent - Multi- Carrier techniques (CMC) have been increased 1,2'3 In HDWDM access to all channels simultaneously is performed by demultiplexers and di- rect detection receivers. In CMC techniques access is performed by tuning the local laser of a heterodyne receiver to a single selected channel (rejecting all others). Switching of a high number of broadband channels (1 ... 10 Gbit /s) is a challenge for different and competiting techniques in future. This paper will contribute to this area by describing an optical solution which makes use of the advantages of the coherent techniques in a proposed CMC- switching node. CMC -SYSTEM CONSIDERATIONS The switching node in Fig. 1 is characterized by N input and output waveguides (fibers) each containing a Coherent - Multi- Carrier (CMC) comb providing M optical channels. The broadband signals modulated onto each input carrier can be switched at each output channel on each output fiber without any electronical signal switching. For the following power budget calculations the Fig. 2 is used. It shows the empirical de- pendence of the minimum detectable power and the bit rate, averaged from a plurality of recent published experiments, either with direct detection and coherent detection techniques. A simple but competitive switching architecture is shown in Fig. 3. Different but only single carriers per input fiber are frequency multiplexed in a star network. Each heterodyne- receiver can have access to each carrier by tuning only its local laser and by making use of the high - frequency- selectivity of the heterodyne- detection scheme 4. 196 / SPIE Vol. 1175 Coherent Lightwave Communications (1989) Broadband Exchange by Coherent Multi-Carrier Switching E.-J. Bachus, R.-P.Braun, C.Caspar, H.M.Foisel, N.Keil, H.H.Yao and B.Strebel Heinrich-Hertz-Institut fur Nachrichtentechnik Berlin GmbH Einsteinufer 37, D-1000 Berlin 10, FRG ABSTRACT A proposed high capacity optical Coherent Multi-Carrier (CMC) switching node for broad- band application is described. The switching of signals is performed in the optical domain by routing the carriers through broadband and selective stars, by frequency conversion and tunable heterodyn-receivers. Experimental results of a switching element are presented and a simple calculation shows, that more than 10,000 broadband carriers could be processed. INTRODUCTION Frequency-multiplex techniques are applied in radio- and microwave-communication links if the bandwidth of the transmission medium is much higher than the bandwidth of a single signaL This is particularly the case in fiber-optic transmission and consequently the investigations in the field of High-Density-Wavelength-Division Multiplex techniques (HDWDM) and Coherent- Multi-Carrier techniques (CMC) have been increased 1|2 ' 3 . In HDWDM access to all channels simultaneously is performed by demultiplexers and di- rect detection receivers. In CMC techniques access is performed by tuning the local laser of a heterodyne receiver to a single selected channel (rejecting all others). Switching of a high number of broadband channels (1 ... 10 Gbit/s) is a challenge for different and competiting techniques in future. This paper will contribute to this area by describing an optical solution which makes use of the advantages of the coherent techniques in a proposed CMC-switching node. CMC-SYSTEM CONSIDERATIONS The switching node in Fig. 1 is characterized by N input and output waveguides (fibers) each containing a Coherent-Multi-Carrier (CMC) comb providing M optical channels. The broadband signals modulated onto each input carrier can be switched at each output channel on each output fiber without any electronical signal switching. For the following power budget calculations the Fig. 2 is used. It shows the empirical de- pendence of the minimum detectable power and the bit rate, averaged from a plurality of recent published experiments, either with direct detection and coherent detection techniques. A simple but competitive switching architecture is shown in Fig. 3. Different but only single carriers per input fiber are frequency multiplexed in a star network. Each heterodyne-receiver can have access to each carrier by tuning only its local laser and by making use of the high- frequency-selectivity of the heterodyne-detection scheme 4 . 196 / SPIE Vol. 1175 Coherent Lightwave Communications (1989) Downloaded From: http://proceedings.spiedigitallibrary.org/ on 02/17/2015 Terms of Use: http://spiedl.org/terms