Suppose we know (from looking at an available volatility surface) the implied volatility (flat volatility) of a cap with a maturity of 10 years and strike of 1%. This would correspond to a cap that's spot starting, correct?
If we instead have a cap with a maturity of 10 years and strike of 1% that becomes active in 1 years time (so the cap runs from year 1-11), what is the correct implied volatility to use to value this? It feels to me that it must be different from the first situation, since we are finding the average volatility over a time period of an interest rate (as expected by the market) and we are now dealing with a separate time period. Would we have to strip the caplet volatilities from the surface and value each caplet contained in the second cap with these caplet volatilities? Or is there a shortcut?