C1C ?copyright 2001, sony electronics inc. all rights reserved. 2.5gbps post amp high bandwidth demand the increasing demand for high-band- width in different application related to the internet, telecommunications, data communi- cations, fiber channel, etc. has created a tremendous need for fiber rich networks and the components that support them. to meet these high bandwidth requirements, the fast product turn-around time dominates the deci- sion-making process for the customer in ven- dor selection. the exponential growth in opti- cal technology, due to these high bandwidth requirements, along with competition in opti- cal components, makes the customer more demanding and specific about the product requirement. ode laser diode sony sony optical fiber optical fiber photo diode pre-amp post-amp cdr de- mux laser diode driver multi- plexer con- verter phase modulation phase modulation switch fabric f igure 1. optical networking block diagram industrys requirements after studying the market, the customer has to decide which component is appropriate for their application. then, they must develop an optical module based on the projects fun- damental requirements such as: ?t ime to market ? better, faster, most cost efficient, and scal- able ? the development cycle ? meet all the standards specifications ? marketing and the technical support provid- ed by the vendor
C2C ? evaluation board availability and above all, the brand name, which is important from service point of view. ? compact package size, if needed available even in wafer form ? complete specification and application notes for the product ? the vendors roadmaps on products in the pipeline. ?a back up solution in case the vendor dis- continues the product qualifying tests qualification of these devices is time con- suming. the customer needs to perform mul- tiple tests, including: ? electro-optical test, which requires several weeks ? life time tests, which takes a few months ? fulfill all standards (itu / bellcore) speci- fications ? check ac / dc characteristics & power consumption ? the vendor provides temperature character- istics and package qualification. why sonys post amp sony has a line of optical communication products and a promising road map including 10gbps follow-on products. based on the cri- teria and concerns, one of the high-perfor- mance optical networking products is our post-amp. this is an ideal product for fiber optics applications. this high-speed post amplifier with signal detector, CXB1820, is part of sonys family of 2.5gbps optical networking ics for use in high-performance optical trans- mitter and receiver functions. it can also be used in fiber channel (2.1gb/s) applications. the sonys CXB1820 has design flexibil- ity and meets the needs for performance, reli- ability, and cost. it comes in a compact 24-pin vqfn plastic package with a fine lead pitch of 0.4mm and has been used in the fiber optics applications. a typical sonet application in which this product can fully utilize its fea- tures is an oc-48 module, giving a data rate 2.488 gbps. about sonys post-amp this bipolar post amplifier has an edge over existing parts in the market and fulfills the industry requirements. the key receiver function provides reshaping and regenerating on a single chip with one power supply of +3.3v. a typical optical communication system needs an alarm function, which asserts the alarm signal at a very low bit error rate (>1e- 3). the signal detector in the CXB1820 will assert an alarm signal at input voltage 2- 4mvpp. the hysteresis width for this chip is designed to maintain a constant gain of 6db whereas the typical values are 3db. this post-amp has the power and chip- count savings that can translate into better uti- lization of the real estate on an optical module
? photo diode pre-amp post-amp w/ signal detect CXB1820 signal detector clock / data recovery de- mux 1:n clock data f igure 2. typical receiver unit for sonet / sdh fiber system or printed circuit board. this leads to cost sav- ings to the designer on both fiber-based data communication and telecom solutions. the typical signal which is received from a pre amplifier is weak, so the post amplifier should have high sensitivity; this high sensitivity is provided in the CXB1820. the evaluation board is equipped with a dual supply capability in order to connect ecl outputs to measuring instruments. other features for the post-amp include: ? auto offset cancel circuit ? signal interruption alarm output ? stabilized signal detect output function ? ttl/ecl/pecl support ? squelch circuit application t ypical applications for the post amp are: ? sonet /sdh transmission systems and modules. ? oc-48 fiber optic modules ? gigabit ethernet ? fiber channel up to 2.1gbps this gives the customer an additional option to choose clock data recovery (cdr) integrated with post-amp or independent cdr. the interface between the post-amp and the cdr is an industry standard. the basic approach to accomplish the cdr adopted is through phase lock loop (pll).
C4C p re-amp photo diode post-amp + clock / data recovery (cxb1826) post-amp cdr signal detector clock data f igure 3. typical receiver unit with integrated post-amp and cdr f or sonet / sdh fiber system conclusions benefits ? available both as post amp and post amp integrated with cdr @ 2.5gbps ? good sensitivity ? stable signal detect function ? signal detect hysteresis width of 6db max ? supports both ttl/pecl output for signal detect as fiber optics data communication prod- ucts, are growing at a rapid pace, higher speeds, compact sizes and increased function- ality is imminent. even though more integra- tion is possible though not desirable in all cases, this provides the customer more room for flexibility. embracing this growing market trend, sony will provide more integrated devices and high-speed optical components that reach up to 10 gbps. these devices will be available in wafer form as well. sonys product roadmap includes products such as post-amp, laser diode driver (ldd), clock & data recovery (cdr) and pre-amp. integrated post amp & clock/ data r ecovery after analyzing the market trends, for high-speed and integration, sony has integrat- ed the post amp with clock and data recovery (cdr) into a single chip, the cxb1826. it comes in a 48-pin vqfn package. with one power supply of 3.3v,the key receiver func- tion inclusive of reshaping and regenerating provides retiming as well. no reference clock is required and current mode logic (cml) mode is added.
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