11. PRACTICAL CASE EXAMPLE

11 PRACTICAL CASE EXAMPLE (I) System Requirements: STM-64: Rb = 9.95328 Gbps ≈ 10 Gbps BER = 10-10 (total/final quality) Lt = 2000 km (end to end) Topology: point to point General Choices —since Lt↑, Rb↑: Single-mode, SI OF Source: LD WDM λ = 1550 nm (EDFAs) PESO - Menos de la décima parte que coaxial INCONVENIENTES - No es capaz de llevar la alimentación (como hace el coaxial)

11 PRACTICAL CASE EXAMPLE (II) We Will Try: N = 10 carriers M = 5 sections. Then: L = 2000/5 = 400 km (per section) OF: Fiber attenuation: αOF = 0.25 dB/km Chromatic dispersion coefficient: M = 5 ps/(km·nm) Polarization dispersion coefficient: PMD = 0.01 ps/(√km) Coil/drum length: lc = 2 km Splice attenuation: αs = 0.1 dB No connectors are used PESO - Menos de la décima parte que coaxial INCONVENIENTES - No es capaz de llevar la alimentación (como hace el coaxial)

11 PRACTICAL CASE EXAMPLE (III) LD: Time response: tr = tf = 20 ps Total power into fiber: PoT = 0 dBm (LDs + MUX) Spectral width: Δλ = 0.5 nm PD: Sensitivity: S0 = -26.5 dBm EDFA: Total output power: PoT = 19 dBm Small signal gain: GEDFA = 24 dB Noise figure: F = 4.2 dB DCU: Insertion attenuation: ADCU = 5 dB Compensation: 300 ps/nm PESO - Menos de la décima parte que coaxial INCONVENIENTES - No es capaz de llevar la alimentación (como hace el coaxial)

11 PRACTICAL CASE EXAMPLE (IV) CALCULATIONS PER SECTION AND CARRIER Power Budget Previous steps: Safe margin 8 dB (data) OF+Splices attenuation Total power is divided into 10 carriers PESO - Menos de la décima parte que coaxial INCONVENIENTES - No es capaz de llevar la alimentación (como hace el coaxial)

11 PRACTICAL CASE EXAMPLE (V) Check if PD receives enough power (one carrier): Does not accomplish. Some EDFAs are needed As it is likely we also need DCUs, we use an equivalent gain, taking into account DCU’s losses From -138 to -26.5, with Ge gain PESO - Menos de la décima parte que coaxial INCONVENIENTES - No es capaz de llevar la alimentación (como hace el coaxial)

11 PRACTICAL CASE EXAMPLE (VI) Distribution of EDFAs and DCUs in a section Since LD has low power per carrier, we put a booster EDFA We put an EDFA before each span (in-line amplifier) After each span, we put a DCU (“postcompensating”) So there is a EDFA+DCU in all intermediate positions, a booster EDFA alone, and a final DCU alone PESO - Menos de la décima parte que coaxial INCONVENIENTES - No es capaz de llevar la alimentación (como hace el coaxial) Actually 6 spans! Booster

11 PRACTICAL CASE EXAMPLE (VII) We should check Span attenuation is similar to EDFA gain minus DCU attenuation Signal levels accomplish with device’s ranges Time Budget From Rb, we calculate system response (tSYS) PESO - Menos de la décima parte que coaxial INCONVENIENTES - No es capaz de llevar la alimentación (como hace el coaxial)

11 PRACTICAL CASE EXAMPLE (VIII) From tSYS, we calculate max. dispersion in fiber Now, we compare with actual dispersion in fiber Therefore, DCUs are needed PESO - Menos de la décima parte que coaxial INCONVENIENTES - No es capaz de llevar la alimentación (como hace el coaxial)

11 PRACTICAL CASE EXAMPLE (IX) We calculate minimum compensation required and total compensation (per span) Our DCU compensates Time budget is right PESO - Menos de la décima parte que coaxial INCONVENIENTES - No es capaz de llevar la alimentación (como hace el coaxial)

11 PRACTICAL CASE EXAMPLE (X) OSNR: In our regeneration section It should be enough. By far, it is the weakest part of the design We can shorten the span (more spans) We can use a more powerful LD We can shorten the section length, making section number greater PESO - Menos de la décima parte que coaxial INCONVENIENTES - No es capaz de llevar la alimentación (como hace el coaxial)

11 PRACTICAL CASE EXAMPLE (XI) TOTAL BER BUDGET Section BER: RX power impairment: From graphic, BERi is very small OSNR impairment: OSNR = 16 dB, and −24 dBm From graphic BERi = 10-12 PESO - Menos de la décima parte que coaxial INCONVENIENTES - No es capaz de llevar la alimentación (como hace el coaxial)

11 PRACTICAL CASE EXAMPLE (XII) PESO - Menos de la décima parte que coaxial INCONVENIENTES - No es capaz de llevar la alimentación (como hace el coaxial)

11 PRACTICAL CASE EXAMPLE (XIII) Total BER: FINAL SYSTEM CONFIGURATION PESO - Menos de la décima parte que coaxial INCONVENIENTES - No es capaz de llevar la alimentación (como hace el coaxial)