code: @Override
  	public RandomVariable getVolatility(int timeIndex, int liborIndex) {
  		// Create a very simple volatility model here
  		double time             = getTimeDiscretization().getTime(timeIndex);
  		double maturity         = getLiborPeriodDiscretization().getTime(liborIndex);
  		double timeToMaturity   = maturity-time;
  
  		double volatilityInstanteaneous;
  		if(timeToMaturity <= 0)
  		{
  			volatilityInstanteaneous = 0;   // This forward rate is already fixed, no volatility
  		}
  		else
  		{
  			volatilityInstanteaneous = a * Math.exp(-b * timeToMaturity);
  		}
  
  		return new RandomVariable(getTimeDiscretization().getTime(timeIndex), volatilityInstanteaneous);
  	}
docs: /* (non-Javadoc)
  @see net.finmath.montecarlo.interestrate.modelplugins.LIBORVolatilityModel#getVolatility(int, int)