Abstract | ||
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To meet increasing demands for server computational power, high-density, multilane links with a data rate exceeding 25Gb/s/lane are needed. An optical transceiver with a retiming capability would significantly enhance the usability of the link by extending the reach. Such optical transceivers should operate without an external clock source since a small form factor is imperative. The optical link we develop has a four-lane configuration that consists of an electrical-to-optical (E/O) converter and an optical-to-electrical (O/E) convertor (Fig. 22.7.1). Both the E/O and O/E convertors are equipped with a per-lane reference-less clock-and-data recovery (CDR) circuit that enables independent operation of each lane. The transceiver pitch is 250μm/lane, which matches the fiber pitch of the optical-fiber array used in the link. Since the jitter added by the CDR should be minimized in retimer applications, an LC-VCO is a preferable choice for clock-signal generation. At this transceiver pitch, however, the coupling through mutual inductances between LC tanks has a significant impact on the CDR characteristics. To address this concern, we analyze the impact of inter-VCO coupling and design the CDR so that the coupling does not affect the CDR performance. Each lane of the E/O convertor consists of a continuous-time linear equalizer (CTLE), a CDR, and a VCSEL driver with a two-tap feed-forward equalizer (FFE) (Fig. 22.7.1). Each lane of the O/E convertor has a trans-impedance amplifier (TIA) stage followed by a limiting amplifier (LA), a CDR, and an electrical-line driver with a two-tap FFE. All the CDRs have an identical design consisting of a flip-flop for the data decision, a selector for bypass-mode operation, a Pottbacker type phase-frequency detector (PFD) [1], a charge pump (CP), a lag-lead filter, and a quadrature LC-VCO (QVCO). During the bypass mode, the CDR loop is set into a power-down mode where the VCO does not oscillate. |
Year | DOI | Venue |
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2015 | 10.1109/ISSCC.2015.7063101 | ISSCC |
Keywords | DocType | Citations |
optical fibers,bandwidth,couplings | Conference | 0 |
PageRank | References | Authors |
0.34 | 2 | 9 |
Name | Order | Citations | PageRank |
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Takayuki Shibasaki | 1 | 66 | 12.00 |
Yukito Tsunoda | 2 | 33 | 7.23 |
Hideki Oku | 3 | 3 | 1.88 |
Satoshi Ide | 4 | 40 | 7.35 |
Toshihiko Mori | 5 | 20 | 6.30 |
Yoichi Koyanagi | 6 | 68 | 13.60 |
Kazuhiro Tanaka | 7 | 3 | 2.22 |
Tomohiro ISHIHARA | 8 | 6 | 2.62 |
Hirotaka Tamura | 9 | 204 | 32.19 |